GIFT   OF 


BIOLOGY 

LIBRARY 

G 


BLAISDELL'S   SERIES  OF  PHYSIOLOGIES 

BY  ALBERT   F.  BLAISDELL,  M.D. 


CHILD'S    BOOK   OF    HEALTH. 

In  easy  lessons  for  primary  grades.     Fully  illustrated.     For  intro- 
duction, 30  cents. 

HOW   TO    KEEP  WELL. 

A  text-book  of  health  for  the  lower  gradet.     For  introduction,  45 
cents. 

OUR    BODIES    AND    HOW  WE    LIVE. 

An  elementary  text-book  of  physiology  and   hygiene  for  use   in 
schools.      For  introduction,  65  cents. 

A    PRACTICAL    PHYSIOLOGY. 

A  text-book  for  higher  schools.     For  introduction,     $1.10. 

HOW   TO   TEACH    PHYSIOLOGY. 

A  handbook  for  teachers.     Paper.     Fully  illustrated.     Price,  10 
cents. 


GINN   &   COMPANY,  PUBLISHERS. 


PRACTICAL  PHYSIOLOGY 


A  TEXT-BOOK  FOR  HIGHER  SCHOOLS 


ALBERT   F.  BLAISDELL,  M.D. 

AUTHOR  OF  "CHILD'S  BOOK  OF  HEALTH,"  "HOW  TO  KEEP  WELL," 

"OUR   BODIES   AND   HOW  WE   LIVE,"   ETC.,   ETC. 


BOSTON,  U.S.A.,  AND  LONDON 
GINN    &    COMPANY,    PUBLISHERS 


1900 


BIOLOGY 
LIBRARY 

3 


A 


COPYRIGHT,  1897,  BY 
ALBERT    F.    BLAISDELL 


ALL   RIGHTS    RESERVED 


PREFACE. 


THE  author  has  aimed  to  prepare  a  text-book  on  human 
physiology  for  use  in  higher  schools.  The  design  of  the  book 
is  to  furnish  a  practical  manual  of  the  more  important  facts 
and  principles  of  physiology  and  hygiene,  which  will  be 
adapted  to  the  needs  of  students  in  high  schools,  normal 
schools,  and  academies. 

Teachers  know,  and  students  soon  learn  to  recognize  the 
fact,  that  it  is  impossible  to  obtain  a  clear  understanding  of 
the  functions  of  the  various  parts  of  the  body  without  first 
mastering  a  few  elementary  facts  about  their  structure.  The 
course  adopted,  therefore,  in  this  book,  is  to  devote  a  certain 
amount  of  space  to  the  anatomy  of  the  several  organs  before 
describing  their  functions. 

A  mere  knowledge  of  the  facts  which  can  be  gained  in 
secondary  schools,  concerning  the  anatomy  and  physiology  of 
the  human  body,  is  of  little  real  value  or  interest  in  itself. 
Such  facts  are  important  and  of  practical  worth  to  young 
students  only  so  far  as  to  enable  them  to  understand  the  rela- 
tion of  these  facts  to  the  great  laws  of  health  and  to  apply 
them  to  daily  living.  Hence,  it  has  been  the  earnest  effort 
of  the  author  in  this  book,  as  in  his  other  physiologies  for 
schools,  to  lay  special  emphasis  upon  such  points  as  bear  upon 
personal  health. 

Physiology  cannot  be  learned  as  it  should  be  by  mere  book 
study.  The  result  will  be  meagre  in  comparison  with  the  capa- 

451362 


iv  PREFACE. 

bilities  of  the  subject.  The  study  of  the  text  should  always 
be  supplemented  by  a  series  of  practical  experiments.  Actual 
observations  and  actual  experiments  are  as  necessary  to  illumi- 
nate the  text  and  to  illustrate  important  principles  in  physi- 
ology as  they  are  in  botany,  chemistry,  or  physics.  Hence,  as 
supplementary  to  the  text  proper,  and  throughout  the  several 
chapters,  a  series  of  carefully  arranged  and  practical  experi- 
ments has  been  added.  For  the  most  part,  they  are  simple  and 
can  be  performed  with  inexpensive  and  easily  obtained  appara- 
tus. They  are  so  arranged  that  some  may  be  omitted  and 
others  added  as  circumstances  may  allow. 

If  it  becomes  necessary  to  shorten  the  course  in  physiology, 
the  various  sections  printed  in  smaller  type  may  be  omitted  or 
used  for  home  study. 

The  laws  of  most  of  the  states  now  require  in  our  public 
schools  the  study  of  the  effects  of  alcoholic  drinks,  tobacco,  and 
other  narcotics  upon  the  bodily  life.  This  book  will  be  found 
to  comply  fully  with  all  such  laws. 

The  author  has  aimed  to  embody  in  simple  and  concise  lan- 
guage the  latest  and  most  trustworthy  information  which  can 
be  obtained  from  the  standard  authorities  on  modern  physiol- 
ogy, in  regard  to  the  several  topics. 

In  the  preparation  of  this  text-book  the  author  has  had  the 
editorial  help  of  his  esteemed  friend,  Dr.  J.  E.  Sanborn,  of 
Melrose,  Mass.,  and  is  also  indebted  to  the  courtesy  of 
Thomas  E.  Major,  of  Boston,  for  assistance  in  revising  the 
proofs. 

ALBERT   F.    BLAISDELL. 

BOSTON,  August,  1897. 


CONTENTS. 


CHAPTER   I. 

INTRODUCTION      .        .        .        ...        . 


CHAPTER   II. 
THE  BONES  ......        .        .        .        .        .        -21 

CHAPTER    III. 
THE  MUSCLES      ...........    57 

CHAPTER    IV. 
PHYSICAL  EXERCISE     .......  -       ...    78 

CHAPTER  V. 
FOOD  AND  DRINK        ..........    97 

CHAPTER  VI. 
DIGESTION    ............  119 

CHAPTER   VII. 
THE  BLOOD  AND  ITS  CIRCULATION    .......  169 

CHAPTER   VIII. 
RESPIRATION        ...........  202 

CHAPTER   IX. 
THE  SKIN  AND  THE  KIDNEYS    ........  235 


VI  CONTENTS. 


CHAPTER    X.  PAGE 

THE  NERVOUS  SYSTEM 263 


CHAPTER   XI. 
THE  SPECIAL  SENSES .  307 

CHAPTER  XII. 
THE  THROAT  AND  THE  VOICE 356 

CHAPTER   XIII. 
ACCIDENTS  AND  EMERGENCIES 367 

CHAPTER   XIV. 

IN  SICKNESS  AND  IN  HEALTH    , 386 

Care  of  the  Sick-Room,  386;  Poisons  and  their  Antidotes,  391; 
Bacteria,  395 ;  Disinfectants,  400  ;  Management  of  Contagious 
Diseases,  402. 

CHAPTER   XV. 

EXPERIMENTAL  WORK  IN  PHYSIOLOGY 405 

Practical  Experiments,  405  ;  Use  of  the  Microscope^  407  ;  Additional 
Experiments,  409;  Surface  Anatomy  and  Landmarks,  415. 

GLOSSARY      .        .        .        .        .• 421 

INDEX 439 


PRACTICAL     PHYSIOLOGY. 

CHAPTER    I. 

INTRODUCTION. 

I.  The  Study  of  Physiology.  We  are  now  to  take  up  a 
new  study,  and  in  a  field  quite  different  from  any  we  have  thus 
far  entered.  Of  all  our  other  studies,  —  mathematics,  physics, 
history,  language,  —  not  one  comes  home  to  us  with  such  pecu- 
liar interest  as  does  physiology,  because  this  is  the  study  of 
ourselves. 

Every  thoughtful  young  person  must  have  asked  himself  ^ 
hundred  questions  about  the  problems  of  human  life  :  how  it 
can  be  that  the  few  articles  of  our  daily  food  —  milk,  bread, 
meats,  and  similar  things  —  build  up  our  complex  bodies,  and 
by  what  strange  magic  they  are  transformed  into  hair,  skin, 
teeth,  bones,  muscles,  and  blood. 

How  is  it  that  we  can  lift  these  curtains  of  our  eyes  an$  behold 
all  the  wonders  of  the  world  around  us,  then  drop  the  lids,  and 
though  at  noonday,  are  instantly  in  total  darkness?  How  does 
the  minute  structure  of  the  ear  report  to  us  with  equal  accuracy 
the  thunder  of  the  tempest,  and  the  hum  of  the  passing  bee  ? 
Why  is  breathing  so  essential  to  our  life,  and  why  cannot  we 
stop  breathing  when  we  try  ?  Where  within  us,  and  how,  burns 
the  mysterious  fire  whose  subtle  heat  warms  us  from  the  first 
breath  of  infancy  till  the  last  hour  of  life  ? 


2  PRACTICAL    PHYSIOLOGY. 

These  and  scores  of  similar  questions  it  is  the  province  of 
this  deeply  interesting  study  of  physiology  to  answer. 

2.  What  Physiology  should  Teach  us.     The  study  of  phys- 
iology is  not  only  interesting,  but  it  is  also  extremely  useful. 
Every  reasonable  person  should  not  only  wish  to  acquire  the 
knowledge  how  best  to  protect   and   preserve  his  body,  but 
should  feel  a  certain  profound  respect  for  an  organism  so  won- 
derful and  so  perfect  as  his  physical  frame.     For  our  bodies 
are  indeed  not  ourselves,  but  the  frames  that  contain  us, — the 
ships  in  which  we,  the  real  selves,  are  borne  over  the  sea  of 
life.     He  must  be  indeed  a  poor  navigator  who  is  not  zealous 
to  adorn  and  strengthen  his  ship,  that  it  may  escape  the  rocks 
of  disease  and  premature  decay,  and  that  the  voyage  of  his  life 
may  be  long,  pleasant,  and  successful. 

But  above  these  thoughts  there  rises  another,  —  that  in  study- 
ing physiology  we  are  tracing  the  myriad  lines  of  marvelous 
ingenuity  and  forethought,  as  they  appear  at  every  glimpse  of 
the  work  of  the  Divine  Builder.  However  closely  we  study  our 
bodily  structure,  we  are,  at  our  best,  but  imperfect  observers 
of  the  handiwork  of  Him  who  made  us  as  we  are. 

3.  Distinctive  Characters  of  Living  Bodies.     Even  a  very 
meagre  knowledge  of  the  structure  and  action  of  our  bodies 
is  enough  to  reveal  the  following  distinctive  characters  :  our 
bodies  are  continually  breathing,  that  is,  they  take  in  oxygen 
from    the   surrounding  air ;    they  take   in   certain   substances 
known  as  food,  similar  Jo  those  composing  the  body,  which  are 
capable  through  a  process  called  oxidation,  or  through  other 
chemical  changes,  of  setting  free  a  certain  amount  of  energy. 

Again,  our  bodies  are  continually  making  heat  and  giving 
it  out  to  surrounding  objects,  the  production  and  the  loss  of 
heat  being  so  adjusted  that  the  whole  body  is  warm,  that  is, 
of  a  temperature  higher  than  that  of  surrounding  objects.  Our 


INTRODUCTION.  3 

bodies,  also,  move  themselves,  either  one  part  on  another,  or 
the  whole  body  from  place  to  place.  The  motive  power  is  not 
from  the  outside  world,  but  the  energy  of  their  movements 
exists  in  the  bodies  themselves,  influenced  by  changes  in  their 
surroundings.  Finally,  our  bodies  are  continually  getting  rid 
of  so-called  waste  matters,  which  may  be  considered  products 
of  the  oxidation  of  the  material  used  as  food,  or  of  the  sub- 
stances which  make  up  the  organism. 

4.  The  Main  Problems  of  Physiology  briefly  Stated.    We 

shall  learn  in  a  subsequent  chapter  that  the  living  body  is  con- 
tinually losing  energy,  but  by  means  of  food  is  continually 
restoring  its  substance  and  replenishing  its  stock  of  energy. 
A  great  deal  of  energy  thus  stored  up  is  utilized  as  mechanical 
work,  the  result  of  physical  movements.  We  shall  learn  later 
on  that  much  of  the  energy  which  at  last  leaves  the  body  as 
heat,  exists  for  a  time  within  the  organism  in  other  forms  than 
heat,  though  eventually  transformed  into  heat.  Even  a  slight 
change  in  the  surroundings  of  the  living  body  may  rapidly, 
profoundly,  and  in  special  ways  affect  not  only  the  amount,  but 
the  kind  of  energy  set  free.  Thus  the  mere  touch  of  a  hair 
may  lead  to  such  a  discharge  of  energy,  that  a  body  previously 
at  rest  may  be  suddenly  thrown  into  violent  convulsions.  This 
is  especially  true  in  the  case  of  tetanus,  or  lockjaw. 

The  main  problem  we  have  to  solve  in  the  succeeding  pages 
is  to  ascertain  how  it  is  that  our  bodies  can  renew  their  sub- 
stance and  replenish  the  energy  which  they  are  continually 
losing,  and  can,  according  to  the  nature  of  their  surroundings, 
vary  not  only  the  amount,  but  the  kind  of  energy  which  they 
set  free. 

5.  Technical   Terms   Defined.      All   living   organisms  are 
studied  usually  from  two  points  of  view :  first,  as  to  their  form 
and  structure ;  second,  as  to  the  processes  which  go  on  within 


4  PRACTICAL    PHYSIOLOGY. 

them.  The  science  which  treats  of  all  living  organisms  is 
called  biology.  It  has  naturally  two  divisions,  —  morphology, 
which  treats  of  the  form  and  structure  of  living  beings,  and 
physiology,  which  investigates  their  functions,  or  the  special 
work  done  in  their  vital  processes. 

The  word  anatomy,  however,  is  usually  employed  instead  of 
morphology.  It  is  derived  from  two  Greek  words,  and  means 
the  science  of  dissection.  Human  anatomy  then  deals  with 
the  form  and  structure  of  the  human  body,  and  describes  how 
the  different  parts  and  organs  are  arranged,  as  revealed  by 
observation,  by  dissection,  and  by  the  microscope. 

Histology  is  that  part  of  anatomy  which  treats  of  the 
minute  structure  of  any  part  of  the  body,  as  shown  by  the 
microscope. 

Human  physiology  describes  the  various  processes  that  go 
on  in  the  human  body  in  health.  It  treats  of  the  work  done 
by  the  various  parts  of  the  body,  and  of  the  results  of  the 
.harmonious  action  of  the  several  organs.  Broadly  speaking, 
physiology  is  the  science  which  treats  of  functions.  By  the 
word  function  is  meant  the  special  work  which  an  organ  has 
to  do.  An  organ  is  a  part  of  the  body  which  does  a  special 
work.  Thus  the  eye  is  the  organ  of  sight,  the  stomach  of 
digestion,  and  the  lungs  of  breathing. 

It  is  plain  that  we  cannot  understand  the  physiology  of  our 
bodies  without  a  knowledge  of  their  anatomy.  An  engineer 
could  not  understand  the  working  of  his  engine  unless  well 
acquainted  with  all  its  parts,  and  the  manner  in  which  they 
were  fitted  together.  So,  if  we  are  to  understand  the  principles 
of  elementary  physiology,  we  must  master  the  main  anatomical 
facts  concerning  the  organs  of  the  body  before  considering 
their  special  functions. 

As  a  branch  of  study  in  our  schools,  physiology  aims  to 
make  clear  certain  laws  which  are  necessary  to  health,  so  that 
by  a  proper  knowledge  of  them,  and  their  practical  applica- 


INTRODUCTION.  5 

tk 

tion,  we  may  hope  to  spend  happier  and  more  useful,  because 
healthier,  lives.  In  brief,  the  study  of  hygiene,  or  the  science 
of  health,  in  the  school  curriculum,  is  usually  associated  with 
that  of  physiology.1 

6.  Chemical  Elements  in  the  Body.  All  of  the  various 
complex  substances  found  in  nature  can  be  reduced  by  chemi- 
cal analysis  to  about  70  elements,  which  cannot  be  further 
divided.  By  various  combinations  of  these  70  elements  all  the 
substances  known  to  exist  in  the  world  of  nature  are  built  up. 
When  the  inanimate  body,  like  any  other  substance,  is  sub- 
mitted to  chemical  analysis,  it  is  found  that  the  bone, 
muscle,  teeth,  blood,  etc.,  may  be  reduced  to  a  few  chemical 
elements. 

In  fact,  the  human  body  is  built  up  with  13  of  the  70 
elements,  namely :  oxygen,  hydrogen,  nitrogen,  chlorine, 
fluorine,  carbon,  phosphorus,  sulphur,  calcium,  potassium, 
sodium,  magnesium,  and  iron.  Besides  these,  a  few  of  the 
other  elements,  as  silicon,  have  been  found ;  but  they  exist  in 
extremely  minute  quantities. 

1  The  Value  of  Physiological  Knowledge.  "  If  any  one  doubts  the  impor- 
tance of  an  acquaintance  with  the  fundamental  principles  of  physiology  as  a  means 
to  complete  living,  let  him  look  around  and  see  how  many  men  and  women  he  can 
find  in  middle  life,  or  later,  who  are  thoroughly  well.  Occasionally  only  do  we  meet 
with  an  example  of  vigorous  health  continued  to  old  age ;  hourly  do  we  meet  with 
examples  of  acute  disorder,  chronic  ailment,  general  debility,  premature  decrepitude. 
Scarcely  is  there  one  to  whom  you  put  the  question,  who  has  not,  in  the  course  of  his 
life,  brought  upon  himself  illness  from  which  a  little  knowledge  would  have  saved 
him.  Here  is  a  case  of  heart  disease  consequent  on  a  rheumatic  fever  that  followed 
a  reckless  exposure.  There  is  a  case  of  eyes  spoiled  for  life  by  overstudy. 

"  Not  to  dwell  on  the  natural  pain,  the  gloom,  and  the  waste  of  time  and  money 
thus  entailed,  only  consider  how  greatly  ill  health  hinders  the  discharge  of  all  duties, 
—  makes  business  often  impossible,  and  always  more  difficult;  produces  irritability 
fatal  to  the  right  management  of  children,  puts  the  functions  of  citizenship  out  of  the 
question,  and  makes  amusement  a  bore.  Is  it  not  clear  that  the  physical  sins  — 
partly  our  ancestors'  and  partly  our  own  —  which  produce  this  ill  health  deduct  more 
from  complete  living  than  anything  else,  and  to  a  great  extent  make  life  a  failure 
and  a  burden,  instead  of  a  benefaction  and  a  pleasure?"  —  HERBERT  SPENCER. 


O  PRACTICAL    PHYSIOLOGY. 

The  following  table  gives  the  proportion  in  which   these 
various  elements  are  present : 

Oxygen 62.430  per  cent 

Carbon 21.150   "  " 

Hydrogen .  9.865   "  " 

Nitrogen 3.100   "  " 

Calcium 1.900   "  " 

Phosphorus .     .  0.946  "  " 

Potassium 0.230  "  " 

Sulphur 0.162   "  " 

Chlorine 0.081    "  " 

Sodium 0.081    "  " 

Magnesium 0.027   "  " 

Iron 0.014   "  " 

Fluorine 0.014  "  «« 


100.000 


As  will  be  seen  from  this  table,  oxygen,  hydrogen,  and  nitro- 
gen, which  are  gases  in  their  uncombined  form,  make  up  f  of 
the  weight  of  the  whole  human  body.  Carbon,  which  exists  in 
an  impure  state  in  charcoal,  forms  more  than  £  of  the  weight 
of  the  body.  Thus  carbon  and  the  three  gases  named,  make 
up  about  96  per  cent  of  the  total  weight  of  the  body. 

7.  Chemical  Compounds  in  the  Body.  We  must  keep  in 
mind  that,  with  slight  exceptions,  none  of  these  13  elements 
exist  in  their  elementary  form  in  the  animal  economy.  They 
are  combined  in  various  proportions,  the  results  differing 
widely  from  the  elements  of  which  they  consist.  Oxygen  and 
hydrogen  unite  to  form  water,  and  water  forms  more  than  §  of 
the  weight  of  the  whole  body.  In  all  the  fluids  of  the  body, 
water  acts  as  a  solvent,  and  by  this  means  alone  the  circulation 
of  nutrient  material  is  possible.  All  the  various  processes  of 
secretion  and  nutrition  depend  on  the  presence  of  water  for 
their  activities. 


INTRODUCTION.  7 

8.  Inorganic  Salts.  t  A  large  number  of  the  elements  of  the 
body  unite  one  with  another  by  chemical  affinity  and  form  inor- 
ganic salts.    Thus  sodium  and  chlorine  unite  and  form  chloride 
of  sodium,  or  common  salt.     This  is  found  in  all  the  tissues 
and  fluids,  and  is  one  of  the  most  important  inorganic  salts  the 
body  contains.  It  is  absolutely  necessary  for  continued  existence. 
By  a  combination  of  phosphorus  with  sodium,  potassium,  cal- 
cium, and  magnesium,  the  various  phosphates  are  formed. 

The  phosphates  of  lime  and  soda  are  the  most  abundant  of 
the  salts  of  the  body.  They  form  more  than  half  the  material 
of  the  bones,  are  found  in  the  teeth  and  in  other  solids  and 
in  the  fluids  of  the  body.  The  special  place  of  iron  is  in  the 
coloring  matter  of  the  blood.  Its  various  salts  are  traced  in 
the  ash  of  bones,  in  muscles,  and  in  many  other  tissues  and 
fluids.  These  compounds,  forming  salts  or  mineral  matters 
that  exist  in  the  body,  are  estimated  to  amount  to  about  6  per 
cent  of  the  entire  weight. 

9.  Organic   Compounds.     Besides  the  inorganic  materials, 
there  exists  in  the  human  body  a  series  of  compound  substances 
formed  of  the  union  of  the  elements  just  described,  but  which 
require  the  agency  of  living  structures.     They  are   built   up 
from  the  elements  by  plants,  and  are  called  organic.     Human 
beings  and  the  lower  animals  take  the  organized  materials  they 
require,  and  build  them  up  in  their  own  bodies  into  still  more 
highly  organized  forms. 

The  organic  compounds  found  in  the  body  are  usually 
divided  into  three  great  classes  : 

i,.  Proteids,  or  albuminous  substances. 

2.  Carbohydrates  (starches,  sugars,  and  gums). 

3.  Fats. 

The  extent  to  which  these  three  great  classes  of  organic  ma- 
terials of  the  body  exist  in  the  animal  and  vegetable  kingdoms, 
and  are  utilized  for  the  food  of  man,  will  be  discussed  in  the 


8  PRACTICAL    PHYSIOLOGY. 

chapter  on  food  (Chapter  V.).  The  Proteids,  because  they 
contain  the  element  nitrogen  and  the  others  do  not,  are  fre- 
quently called  nitrogenous,  and  the  other  two  are  known  as 
non-nitrogenous  substances.  The  proteids,  the  type  of  which 
is  egg  albumen,  or  the  white  of  egg,  are  found  in  muscle  and 
nerve,  in  glands,  in  blood,  and  in  nearly  all  the  fluids  of  the 
body.  A  human  body  is  estimated  to  yield  on  an  average 
about  1 8  per  cent  of  albuminous  substances.  In  the  succeed- 
ing chapters  we  shall  have  occasion  to  refer  to  various  and 
allied  forms  of  proteids  as  they  exist  in  muscle  (myosin), 
coagulated  blood  (fibrin),  and  bones  (gelatin). 

The  Carbohydrates  are  formed  of  carbon,  hydrogen,  and 
oxygen,  the  last  two  in  the  proportion  to  form  water.  Thus  we 
have  animal  starch,  or  glycogen,  stored  up  in  the  liver.  Sugar, 
as  grape  sugar,  is  also  found  in  the  liver.  The  body  of  an  average 
.  man  contains  about  10  per  cent  of  Fats.  These  are  formed  of 
carbon,  hydrogen,  and  oxygen,  in  which  the  latter  two  are  not 
in  the  proportion  to  form  water.  The  fat  of  the  body  consists 
of  a  mixture  which  is  liquid  at  the  ordinary  temperature. 

Now  it  must  not  for  one  moment  be  supposed  that  the 
various  chemical  elements,  as  the  proteids,  the  salts,  the  fats, 
etc.,  exist  in  the  body  in  a  condition  to  be  easily  separated  one 
from  another.  Thus  a  piece  of  muscle  contains  all  the  various 
organic  compounds  just  mentioned,  but  they  are  combined,  and 
in  different  cases  the  amount  will  vary.  Again,  fat  may  exist 
in  the  muscles  even  though  it  is  not  visible  to  the  naked  eye, 
and  a  microscope  is  required  to  show  the  minute  fat  cells. 

10.  Protoplasm.  The  ultimate  elements  of  which  the  body 
is  composed  consist  of  "  masses  of  living  matter,"  microscopic 
in  size,  of  a  material  commonly  called  protoplasm.1  In  its 

1  The  word  protoplasm  must  not  be  misunderstood  to  mean  a  substance  of  a 
definite  chemical  nature,  or  of  an  invariable  morphological  structure ;  it  is  applied  to 
any  part  of  a  cell  which  shows  the  properties  of  life,  and  is  therefore  only  a  conve- 
nient abbreviation  for  the  phrase  "  mass  of  living  matter." 


INTRODUCTION.  9 

simplest  form  protoplasm  appears  to  be  a  homogeneous,  struc- 
tureless material,  somewhat  resembling  the  raw  white  of  an 
egg.  It  is  a  mixture  of  several  chemical  substances  and  differs 
in  appearance  and  composition  in  different  parts  of  the  body. 

Protoplasm  has  the  power  of  appropriating  nutrient  material, 
of  dividing  and  subdividing,  so  as  to  form  new  masses  like 
itself.  When  not  built  into  a  tissue,  it  has  the  power  of  chang- 
ing its  shape  and  of  moving  from  place  to  place,  by  means  of 
the  delicate  processes  which  it  puts  forth.  Now,  while  there 
are  found  in  the  lowest  realm  of  animal  life,  organisms  like 
the  amoeba  of  stagnant  pools,  consisting  of  nothing  more  than 
minute  masses  of  protoplasm,  there  are 
others  like  them  which  possess  a  small 
central  body  called  a  nucleus.  This  is 
known  as  nucleated  protoplasm. 


II.    Cells.     When  we  carry  back  the 
analysis  of  an  organized  body  as  far  as 
we  can,  we  find  every  part  of  it  made  up   FiG.i.-Diagr^mof  a  Cell. 
of   masses   of   nucleated    protoplasm    of      A,  nucleus;  B, 


various  sizes  and  shapes.     In  all  essential      c>  protoplasm.      (Highly 

magnified.) 

features  these  masses  conform  to  the  type 

of  protoplasmic  matter  just  described.  Such  bodies  are  called 
cells.  In  many  cells  the  nucleus  is  finely  granular  or  reticu- 
lated in  appearance,  and  on  the  threads  of  the  meshwork  may 
be  one  or  more  enlargements,  called  nucleoli.  In  some  cases 
the  protoplasm  at  the  circumference  is  so  modified  as  to  give 
the  appearance  of  a  limiting  membrane  called  the  cell  wall.  In 
brief,  then,  a  cell  is  a  mass  of  nucleated  protoplasm  ;  the 
nucleus  may  have  a  nucleolus,  and  the  cell  may  be  limited  by  a 
cell  wall.  Every  tissue  of  the  human  body  is  formed  through 
the  agency  of  protoplasmic  cells,  although  in  most  cases  the 
changes  they  undergo  are  so  great  that  little  evidence  remains 
of  their  existence. 


IO  PRACTICAL    PHYSIOLOGY. 

There  are  some  organisms  lower  down  in  the  scale,  whose 
whole  activity  is  confined  within  the  narrow  limits  of  a  single 
cell.  Thus,  the  amoeba  begins  its  life  as  a  cell  split  off  from  its 
parent.  This  divides  in  its  turn,  and  each  half  is  a  complete 
amoeba.  When  we  come  a  little  higher  than  the  amoeba,  we  find 
organisms  which  consist  of  several  cells,  and  a  specialization 
of  function  begins  to  appear.  As  we  ascend  in  the  animal 
scale,  specialization  of  structure  and  of  function  is  found  con- 
tinually advancing,  and  the  various  kinds  of  cells  are  grouped 
together  into  colonies  or  organs. 

12.  Cells  and  the  Human  Organism.  If  the  body  be 
studied  in  its  development,  it  is  found  to  originate  from  a  single 
mass  of  nucleated  protoplasm,  a  single  cell  with  a  nucleus  and 


FIG.  2. —  Amoeboid  Movement  of  a  Human  White  Blood  Corpuscle. 
(Showing  various  phases  of  movement.) 

nucleolus.  From  this  original  cell,  by  growth  and  development, 
the  body,  with  all  its  various  tissues,  is  built  up.  Many  fully 
formed  organs,  like  the  liver,  consist  chiefly  of  cells.  Again, 
the  cells  are  modified  to  form  fibers,  such  as  tendon,  muscle, 
and  nerve.  Later  on,  we  shall  see  the  white  blood  corpuscles 
exhibit  all  the  characters  of  the  amoeba  (Fig.  2).  Even  such 
dense  structures  as  bone,  cartilage,  and  the  teeth  are  formed 
from  cells. 

In  short,  cells  may  be  regarded  as  the  histological  units  of 
animal  Structures  ;  by  the  combination,  association,  and  modi- 
fication of  these  the  body  is  built  up.  Of  the  real  nature  of 
the  changes  going  on  within  the  living  protoplasm,  the  process 
of  building  up  lifeless  material  into  living  structures,  and  the 


INTRODUCTION.  1 1 

process  of  breaking  down  by  which  waste  is  produced,  we  know 
absolutely  nothing.  Could  we  learn  that,  perhaps  we  should 
know  the  secret  of  life. 

13.  Kinds  of  Cells.     Cells  vary  greatly  in  size,  some  of 
the  smallest  being  only  ^^QTF  °^  an  *ncn  or  ^ess  m  diameter. 
They  also  vary  greatly  in  form,  as  maybe  seen  in  Figs.  3  and  5. 
The  typical  cell  is  usually  globular  in  form,  other  shapes  being 
the  result  of  pressure  or  of  similar  modifying  influences.     The 
globular,  as  well  as  the  large,  flat  cells,  are  well  shown  in  a 
drop  of  saliva.     Then  there  are  the  columnar  cells,  found  in 
various   parts   of   the   intestines,    in   which   they   are   closely 
arranged  side  by  side.    These  cells  sometimes  have  on  the  free 
surface  delicate  prolongations  called  cilia.     Under  the  micro- 
scope they  resemble  a  wave,   as  when  the  wind  blows  over 
a  field  of  grain  (Fig.  5).     There  are  besides  cells  known  as 
spindle,  stellate,  squamous  or  pavement,  and  various  other  names 
suggested  by  their  shapes.     Cells  are  also  described  as  to  their 
contents.     Thus  fat  and  pigment  cells   are   alluded  to  in  suc- 
ceeding   sections.     Again,  they  may  be  described  as  to  their 
functions   or  location   or  the  tissue  in  which  they  are  found, 
as  epithelial  cells,   blood   cells   (corpuscles,   Figs.   2    and    66), 
nerve  cells  (Fig.  4),  and  connective-tissue  cells. 

14.  Vital  Properties  of  Cells.     Each  cell  has  a  life  of  its 
own.     It  manifests  its  vital  properties  in  that  it  is  born,  grows, 
multiplies,  decays,  and  at  last  dies.1     During  its  life  it  assimi- 
lates food,  works,  rests,  and  is  capable  of  spontaneous  motion 

1  "  Did  we  possess  some  optic  aid  which  should  overcome  the  grossness  of  our 
vision,  so  that  we  might  watch  the  dance  of  atoms  in  the  double  process  of  making 
and  unmaking  in  the  living  body,  we  should  see  the  commonplace,  lifeless  things 
which  are  brought  by  the  blood,  and  which  we  call  food,  caught  up  into  and  made 
part  of  the  molecular  whorls  of  the  living  muscle,  linked  together  for  a  while  in  the 
intricate  figures  of  the  dance  of  life,  giving  and  taking  energy  as  they  dance,  and  then 
we  should  see  how,  loosing  hands,  they  slipped  back  into  the  blood  as  dead,  inert, 
used-up  matter."  —  MICHAEL  FOSTER,  Professor  of  Physiology  in  the  University 
of  Cambridge,  England. 


12 


PRACTICAL    PHYSIOLOGY. 


and  frequently  of  locomotion.  The  cell  can  secrete  and  excrete 
substance,  and,  in  brief,  presents  nearly  all  the  phenomena  of 
a  human  being. 

Cells  are  produced  only  from  cells  by  a  process  of  self-divi- 
sion, consisting  of  a  cleavage  of  the  whole  cell  into  parts,  each 
of  which  becomes  a  separate  and  independent  organism.  Cells 
rapidly  increase  in  size  up  to  a  certain  definite  point  which 
they  maintain  during  adult  life.  A  most  interesting  quality  of 

cell  life  is  motion,  a  beauti- 
ful form  of  which  is  found 
in  ciliated  epithelium.  Cells 
may  move  actively  and  pas- 
sively. In  the  blood  the 
cells  are  swept  along  by  the 
current,  but  the  white  cor- 
puscles seem  able  to  make 
their  way  actively  through 
the  tissues,  as  if  guided  by 
some  sort  of  instinct. 

Some  cells  live  a  brief  life 
of  12  to  24  hours,  as  is  prob- 
ably the  case  with  many  of  the  cells  lining  the  alimentary  canal ; 
others  may  live  for  years,  as  do  the  cells  of  cartilage  and  bone. 
In  fact  each  cell  goes  through  the  same  cycle  of  changes  as 
the  whole  organism,  though  doubtless  in  a  much  shorter  time. 
The  work  of  cells  is  of  the  most  varied  kind,  and  embraces  the 
formation  of  every  tissue  and  product,  —  solid,  liquid,  or  gaseous. 
Thus  we  shall  learn  that  the  cells  of  the  liver  form  bile,  those 
of  the  salivary  glands  and  of  the  glands  of  the  stomach  and 
pancreas  form  juices  which  aid  in  the  digestion  of  food. 

15.  The  Process  of  Life.  All  living  structures  are  subject 
to  constant  decay.  Life  is  a  condition  of  incessant  changes, 
dependent  upon  two  opposite  processes,  repair  and  decay. 


FIG.  3. —  Various  Forms  of  Cells. 

A,  columnar  cells  found  lining  various  parts  of 
the  intestines  (called  columnar  epithelium); 
B,  cells  of  a  fusiform  or  spindle  shape  found 
in  the  loose  tissue  under  the  skin  and  in  other 
parts  (called  connective-tissue  cells);  C,  cell 
having  many  processes  or  projections  —  such 
are  found  in  connective  tissue ;  D,  primitive 
cells  composed  of  protoplasm  with  nucleus, 
and  having  no  cell  wall.  All  are  represented 
about  400  times  their  real  size. 


INTRODUCTION.  13 

Thus  our  bodies  are  not  composed  of  exactly  the  same  particles 
from  day  to  day,  or  even  from  one  moment  to  another,  although 
to  all  appearance  we  remain  the  same  individuals.  The  change 
is  so  gradual,  and  the  renewal  of  that  which  is  lost  may  be  so 
exact,  that  no  difference  can  be  noticed  except  at  long  intervals 
of  time.1  (See  under  "  Bacteria,"  Chapter  XIV.) 

The  entire  series  of  chemical  changes  that  take  place  in  the 
living  body,  beginning  with  assimilation  and  ending  with  excre- 
tion, is  included  in  one  word,  metabolism.  The  process  of 
building  up  living  material,  or  the  change  by  which  complex 
substances  (including  the  living  matter  itself)  are  built  up  from 
simpler  materials,  is  called  anabolism.  The  breaking  down 
of  material  into  simple  products,  or  the  changes  in  which 
complex  materials  (including  the  living  substance)  are  broken 
down  into  comparatively  simple  products,  is  known  as  katabol- 
ism.  This  reduction  of  complex  substances  to  simple,  results 
in  the  production  of  animal  force  and  energy.  Thus  a  complex 
substance,  like  a  piece  of  beef-steak,  is  built  up  of  a  large 
number  of  molecules  which  required  the  expenditure  of  force 
or  energy  to  store  up.  Now  when  this  material  is  reduced  by 
the  process  of  digestion  to  simpler  bodies  with  fewer  molecules, 
such  as  carbon  dioxid,  urea,  and  water,  the  force  stored  up  in 
the  meat  as  potential  energy  becomes  manifest  and  is  used  as 
active  life-force  known  as  kinetic  energy. 

16.  Epithelium.  Cells  are  associated  and  combined  in 
many  ways  to  form  a  simple  tissue.  Such  a  simple  tissue  is 
called  an  epithelium  or  surface-limiting  tissue,  and  the  cells 

1  "  Our  material  frame  is  composed  of  innumerable  atoms,  and  each  separate  and 
individual  atom  has  its  birth,  life,  and  death,  and  then  its  removal  from  the  '  place 
of  the  living.'  Thus  there  is  going  on  a  continuous  process  of  decay  and  death 
among  the  individual  atoms  which  make  up  each  tissue.  Each  tissue  preserves  its 
vitality  for  a  limited  space  only,  is  then  separated  from  the  tissue  of  which  it  has 
formed  a  part,  and  is  resolved  into  its  inorganic  elements,  to  be  in  due  course  elimi- 
nated from  the  body  by  the  organs  of  excretion."  —  MACLAREN'S  Physical  Education. 


14  PRACTICAL    PHYSIOLOGY. 

are  known  as  epithelial  cells.  These  are  united  by  a  very 
small  amount  of  a  cement  substance  which  belongs  to  the  pro- 
teid  class  of  material.  The  epithelial  cells,  from  their  shape, 
are  known  as  squamous,  columnar,  glandular,  or  ciliated.  Again, 
the  cells  may  be  arranged  in  only  a  single  layer,  or  they  may 
be  several  layers  deep.  In  the  former  case  the  epithelium  is 
said  to  be  simple ;  in  the  latter,  stratified,  No  blood-vessels 
pass  into  these  tissues  ;  the  cells  derive  their  nourishment  by  the 

imbibition  of  the  plasma  of  the  blood 
exuded  into  the  subjacent  tissue. 


17.  Varieties  of  Epithelium. 
The  squamous  or  pavement  epithe- 
lium consists  of  very  thin,  flattened 
scales,  usually  with  a  small  nucleus 
FIG.  4.  — Nerve  Cells  from  the     in  the  center.      When  the   nucleus 
GrayMatteroftheCerebellum.      hag  disappeared    they  become   mere 
(Magnified  260  diameters.)  .         J 

horny  plates,  easily  detached.  Such 

cells  will  be  described  as  forming  the  outer  layer  of  the  skin, 
the  lining  of  the  mouth  and  the  lower  part  of  the  nostrils. 

The  columnar  epithelium  consists  of  pear-shaped  or  elon- 
gated cells,  frequently  as  a  single  layer  of  cells  on  the  surface 
of  a  mucous  membrane,  as  on  the  lining  of  the  stomach  and 
intestines,  and  the  free  surface  of  the  windpipe  and  large  air- 
tubes. 

The  glandular  or  spheroidal  epithelium  is  composed  of 
round  cells  or  such  as  become  angular  by  mutual  pressure. 
This  kind  forms  the  lining  of  glands  such  as  the  liver,  pan- 
creas, and  the  glands  of  the  skin. 

The  ciliated  epithelium  is  marked  by  the  presence  of  very 
fine  hair-like  processes  called  cilia,  which  develop  from  the  free 
end  of  the  cell  and  exhibit  a  rapid  whip-like  movement  as  long 
as  the  cell  is  alive.  This  motion  is  always  in  the  same  direc- 
tion, and  serves  to  carry  away  mucus  and  even  foreign  particles 


INTRODUCTION. 


in  contact  with  the  membrane  on  which  the  cells  are  placed. 
This  epithelium  is  especially  common  in  the  air  passages,  where 
it  serves  to  keep  a  free  passage  for  the  entrance  and  exit  of 
air.  In  other  canals  a  similar  office  is  filled  by  this  kind  of 
epithelium. 

1 8.  Functions  of  Epithelial  Tissues.  The  epithelial  struc- 
tures may  be  divided,  as  to  their  functions,  into  two  main  divi- 
sions. One  is  chiefly  protective 
in  character.  Thus  the  layers 
of  epithelium  which  form  the 
superficial  layer  of  the  skin  have 
little  beyond  such  an  office  to 
discharge.  The  same  is  to  a 
certain  extent  true  of  the  epi- 
thelial cells  covering  the  mucous 
membrane  of  the  mouth,  and 
those  lining  the  air  passages 
and  air  cells  of  the  lungs. 

The  second  great  division  of 
the  epithelial  tissues  consists 
of  those  whose  cells  are  formed 


FIG.  5.  —  Various  Kinds  of  Epithelial 
Cells. 


r  t  .    i  ,  .  ,  ,A,     columnar  cells   of   intestine ;    B,  poly- 

Of  highly  active  protoplasm,  and      hedral  cells  of  the  conjunctiva;   C,  cili- 

ated  conical  cells  of  the  trachea ;  0, 
ciliated  cell  of  frog's  mouth ;  E,  inverted 
conical  cell  of  trachea ;  F,  squamous  cell 
of  the  cavity  of  mouth,  seen  from  its  broad 
surface  ;  G,  squamous  cell,  seen  edgeways. 


are  busily  engaged  in  some  sort 

of  secretion.    Such  are  the  cells 

of   glands,  —  the    cells    of   the 

salivary  glands,   which  secrete 

the   saliva,   of  the  gastric   glands,    which   secrete   the  gastric 

juice,  of  the  intestinal  glands,  and  the  cells  of  the  liver  and 

sweat  glands. 

19.  Connective  Tissue.  This  is  the  material,  made  up  of 
fibers  and  cells,  which  serves  to  unite  and  bind  together  the 
different  organs  and  tissues.  It  forms  a  sort  of  flexible  frame- 
work of  the  body,  and  so  pervades  every  portion  that  if  all  the 


1 6  PRACTICAL    PHYSIOLOGY. 

other  tissues  were  removed,  we  should  still  have  a  complete 
representation  of  the  bodily  shape  in  every  part.  In  general, 
the  connective  tissues  proper  act  as  packing,  binding,  and  sup- 
porting structures.  This  name  includes  certain  tissues  which 
to  all  outward  appearance  vary  greatly,  but  which  are  properly 
grouped  together  for  the  following  reasons  :  first,  they  all 
act  as  supporting  structures  ;  second,  under  certain  conditions 
one  may  be  substituted  for  another  ;  third,  in  some  places 
they  merge  into  each  other. 

All  these  tissues  consist  of  a  ground-substance,  or  matrix, 
cells,  and  fibers.  The  ground-substance  is  in  small  amount  in 
connective  tissues  proper,  and  is  obscured  by  a  mass  of  fibers. 
It  is  best  seen  in  hyaline  cartilage,  where  it  has  a  glossy 
appearance.  In  bone  it  is  infiltrated  with  salts  which  give 
bone  its  hardness,  and  make  it  seem  so  unlike  other  tissues. 
The  cells  are  called  connective-tissue  corpuscles,  cartilage  cells, 
and  bone  corpuscles,  according  to  the  tissues  in  which  they 
occur.  The  fibers  are  the  white  fibrous  and  the  yellow  elastic 
tissues. 

The  following  varieties  are  usually  described  : 

1 .  White  Fibrous  Tissue. 

2.  Yellow  Elastic  Tissue. 

I.    Connective  Tissues  Areolar  or  Cellular  Tissue. 


Proper : 


4-     Adipose  or  Fatty  Tissue. 
5.    Adenoid  or  Retiform  Tissue. 


{i .    Hyaline. 
2.    White  Fibro-cartilage. 
3.    Yellow  Fibro-cartilage. 

III.     Bone  and  Dentine  of  Teeth. 

20.  White  Fibrous  Tissue.  This  tissue  consists  of  bundles 
of  very  delicate  fibrils  bound  together  by  a  small  amount  of 
cement  substance.  Between  the  fibrils  protoplasmic  masses 


INTRODUCTION. 


(connective-tissue  corpuscles)  are  found.  These  fibers  may  b6 
found  so  interwoven  as  to  form  a  sheet,  as  in  the  periosteum 
of  the  bone,  the  fasciae  around  muscles,  and  the  capsules  of 
organs;  or  they  may  be  aggregated  into  bundles  and  form  rope- 
like  bands,  as  in  the  ligaments 
of  joints  and  the  tendons  of 
muscles.  On  boiling,  this  tis- 
sue yields  gelatine.  In  general, 
where  white  fibrous  tissue 
abounds,  structures  are  held  to- 
gether, and  there  is  flexibility, 
but  little  or  no  distensibility. 

FIG.  6.— White  Fibrous  Tissue. 

21.  YellOW  Elastic  Tissue.  (Highly  magnified.) 

The  fibers  of  yellow  elastic 

tissue  are  much  stronger  and  coarser  than  those  of  the  white. 

They  are  yellowish,  tend  to  curl  up  at  the  ends,  and  are  highly 

elastic.  It  is  these  fibers  which  give  elasticity  to  the  skin  and 

to  the  coats  of  the  arteries.  The 
typical  form  of  this  tissue  occurs  in 
the  ligaments  which  bind  the  verte- 
brae together  (Fig.  26),  in  the  true 
vocal  cords,  and  in  certain  ligaments 
of  the  larynx.  In  the  skin  and  fasciae, 
the  yellow  elastic  is  found  mixed 
with  white  fibrous  and  areolar  tis- 

FIG.  7.- Yellow  Elastic  Tissue.     sues-     It:  does  not  Yield  gelatine  on 
(Highly  magnified.)  boiling,  and  the  cells  are,  if  any,  few. 

22.  Areolar  or  Cellular  Tissue.     This  consists  of  bundles 
of  delicate  fibers  interlacing  and  crossing  one  another,  forming 
irregular  spaces  or  meshes.     These  little  spaces,  in  health,  are 
filled  with  fluid  that  has  oozed  out  of  the  blood-vessels.     The 
areolar  tissue  forms  a  protective  covering  for  the  tissues  of 
delicate  and  important  organs. 


1 8  PRACTICAL    PHYSIOLOGY. 

23.   Adipose  or  Fatty  Tissue.     In  almost  every  part  of  the 
body  the  ordinary  areolar  tissue  contains  a  variable  quantity  of 
adipose  or  fatty  tissue.     Examined  by  the  microscope,  the  fat 
cells  consist  of  a  number  of  minute  sacs  of  exceedingly  delicate, 
structureless  membrane  filled  with  oil.     This  is  liquid  in  life, 
but  becomes  solidified  after  death.     This  tissue  is  plentiful  be- 
neath the  skin,  in  the  abdominal  cavity,  on  the  surface  of  the 
heart,  around  the  kidneys,  in  the  marrow 
p-f^      i   of  bones,  and  elsewhere.     Fat  serves  as 
a  soft  packing  material.     Being  a  poor 
conductor,  it  retains  the  heat,  and  fur- 
nishes a  store  rich  in  carbon  and  hydro- 
gen for  use  in  the  body. 


24.  Adenoid    or    Retiform    Tissue. 
This  is  a  variety  of   connective  tissue 
found  in  the  tonsils,  spleen,  lymphatic 
FIG.  8.  —  Fibro-Cartiiage  Fi-  glands,  and   allied  structures.     It  con- 

bers.  (Showing  network  sur-    sists    Qf    a   yery   fine     network    of    fibrils 
rounding  cartilage  cells.)  .       .  .    .    J  , .         . 

around  which  are  cells  of  various  sizes. 

The  tissue  combining  them  is  known  as  adenoid  or  gland-like 
tissue. 

25.  Cartilage.  Cartilage,  or  gristle,  is  a  tough  but  highly 
elastic  substance.  Under  the  microscope  cartilage  is  seen  to 
consist  of  a  matrix,  or  base,  in  which  nucleated  cells  abound, 
either  singly  or  in  groups.  It  has  sometimes  a  fine  ground- 
glass  appearance,  when  the  cartilage  is  spoken  of  as  hyaline. 
In  other  cases  the  matrix  is  almost  replaced  by  white  fibrous 
tissue.  This  is  called  white  fibro-cartilage,  and  is  found 
where  great  strength  and  a  certain  amount  of  rigidity  are 
required. 

Again,  there  is  between  the  cells  a  meshwork  of  yellow 
elastic  fibers,  and  this  is  called  yellow  fibro-cartilage  (Fig.  8). 
The  hyaline  cartilage  forms  the  early  state  of  most  of  the 


INTRODUCTION. 


bones,  and  is  also  a  permanent  coating 
for  the  articular  ends  of  long  bones. 
The   white   fibro-cartilage   is  found  in     A 
the  disks  between  the  bodies  of  the  ver-     B 
tebrae,  in  the  interior  of  the  knee  joint,     c 
in  the  wrist  and  other  joints,  filling  the 
cavities  of  the  bones,  in  socket  joints, 
and  in  the  grooves  for  tendons.     The 
yellow    fibro-cartilage    forms    the    ex- 
panded part  of  the  ear,  the  epiglottis, 
and  other  parts  of  the  larynx. 

26.  General  Plan  of  the  Body.  To 
get  a  clearer  idea  of  the  general  plan 
on  which  the  body  is  constructed,  let 
us  imagine  its  division  into  perfectly 
equal  parts,  one  the  right  and  the  other 
the  left,  by  a  great  knife  severing  it 
through  the  median,  or  middle  line  in 
front,  backward  through  the  spinal 
column,  as  a  butcher  divides  an  ox  or 
a  sheep  into  halves  for  the  market.  In 
a  section  of  the  body  thus  planned  the 
skull  and  the  spine  together  are  shown 
to  have  formed  a  tube,  containing  the 
brain  and  spinal  cord.  The  other  parts 
of  the  body  form  a  second  tube  (ven- 
tral) in  front  of  the  spinal  or  dorsal 
tube.  The  upper  part  of  the  second 
tube  begins  with  the  mouth  and  is 
formed  by  the  ribs  and  breastbone. 
Below  the  chest  in  the  abdomen,  the 
walls  of  this  tube  would  be  made  up 
of  the  soft  parts. 


D       ..  V- 


FIG.  9. — Diagrammatic  Lon- 
gitudinal Section  of  the 
Trunk  and  Head.  (Show- 
ing the  dorsal  and  the  ven- 
tral tubes.) 

A,  the  cranial  cavity;  B,  the 
cavity  of  the  nose;  C,  the 
mouth ;  D,  the  alimentary 
canal  represented  as  a  simple 
straight  tube  ;  E,  the  sympa- 
thetic nervous  system ;  F, 
heart;  G,  diaphragm;  H, 
stomach ;  K,  end  of  spinal 
portion  of  cerebro-spinal  ner- 
vous system. 


2O  PRACTICAL    PHYSIOLOGY. 

We  may  say,  then,  that  the  body  consists  of  two  tubes  or 
cavities,  separated  by  a  bony  wall,  the  dorsal  or  nervous  tube, 
so  called  because  it  contains  the  central  parts  of  the  nervous 
system  ;  and  the  visceral  or  ventral  tube,  as  it  contains  the 
viscera,  or  general  organs  of  the  body,  as  the  alimentary  canal, 
the  heart,  the  lungs,  the  sympathetic  nervous  system,  and  other 
organs. 

The  more  detailed  study  of  the  body  may  now  be  begun  by 
a  description  of  the  skeleton  or  framework  which  supports  the 
soft  parts. 

EXPERIMENTS. 

For  general  directions  and  explanations  and  also  detailed 
suggestions  for  performing  experiments,  see  Chapter  XV. 

Experiment  i.  To  examine  squamous  epithelium.  With  an  ivory 
paper-knife  scrape  the  back  of  the  tongue  or  the  inside  of  the  lips  or  cheek  ; 
place  the  substance  thus  obtained  upon  a  glass  slide  ;  cover  it  with  a  thin 
cover-glass,  and  if  necessary  add  a  drop  of  water.  Examine  with  the 
microscope,  and  the  irregularly  formed  epithelial  cells  will  be  seen. 

Experiment  2.  To  examine  ciliated  epithelium.  Open  a  frog's  mouth, 
and  with  the  back  of  a  knife  blade  gently  scrape  a  little  of  the  membrane 
from  the  roof  of  the  mouth.  Transfer  to  a  glass  slide,  add  a  drop  of  salt 
solution,  and  place  over  it  a  cover-glass  with  a  hair  underneath  to  prevent 
pressure  upon  the  cells.  Examine  with  a  microscope  under  a  high  power. 
The  cilia  move  very  rapidly  when  quite  fresh,  and  are  therefore  not  easily 
seen. 

For  additional  experiments  which  pertain  to  the  microscopic 
examination  of  the  elementary  tissues  and  to  other  points  in 
practical  histology,  see  Chapter  XV. 

NOTE.  Inasmuch  as  most  of  the  experimental  work  of  this  chapter  depends 
upon  the  use  of  the  microscope  and  also  necessarily  assumes  a  knowledge  of  facts 
which  are  discussed  later,  it  would  be  well  to  postpone  experiments  in  histology  until 
they  can  be  more  satisfactorily  handled  in  connection  with  kindred  topics  as  they  are 
met  with  in  the  succeeding  chapters. 


CHAPTER    II. 
THE  BONES. 

27.  The  Skeleton.     Most  animals  have  some  kind  of  frame- 
work to  support  and  protect  the  soft  and  fleshy  parts  of  their 
bodies.     This  framework  consists  chiefly  of  a  large  number  of 
bones,  and  is  called  the  skeleton.      It  is  like  the  keel  and  ribs 
of  a  vessel  or  the  frame  of  a  house,  the  foundation  upon  which 
the  bodies  are  securely  built. 

There  are  in  the  adult  human  body  200  distinct  bones,  of  many 
sizes  and  shapes.  This  number  does  not,  however,  include 
several  small  bones  found  in  the  tendons  of  muscles  and  in  the 
ear.  The  teeth  'are  not  usually  reckoned  as  separate  bones, 
being  a  part  of  the  structure  of  the  skin. 

The  number  of  distinct  bones  varies  at  different  periods  of 
life.  It  is  greater  in  childhood  than  in  adults,  for  many  bones 
which  are  then  separate,  to  allow  growth,  afterwards  become 
gradually  united.  In  early  adult  life,  for  instance,  the  skull 
contains  22  naturally  separate  bones,  but  in  infancy  the  number 
is  much  greater,  and  in  old  age  far  less. 

The  bones  of  the  body  thus  arranged  give  firmness,  strength, 
and  protection  to  the  soft  tissues  and  vital  organs,  and  also 
form  levers  for  the  muscles  to  act  upon. 

28.  Chemical  Composition  of  Bone.     The  bones,  thus  form- 
ing the  framework  of  the  body,  are  hard,  tough,  and  elastic. 
They  are  twice  as  strong  as  oak ;  one  cubic  inch  of  compact 
bone  will  support  a  weight  of  5000  pounds.     Bone  is  composed 
of  earthy  or  mineral  matter  (chiefly  in  the  form  of  lime  salts), 
and  of  animal  matter  (principally  gelatine),  in  the  proportion 
of  two-thirds  of  the  former  to  one-third  of  the  latter. 


22 


PRACTICAL    PHYSIOLOGY. 


FIG.  io.—  The  Skeleton. 


THE    BONES. 


The  proportion  of  earthy  to  animal  matter  varies  with  age. 
In  infancy  the  bones  are  composed  almost  wholly  of  animal 
matter.  Hence,  an  infant's  bones  are  rarely  broken,  but  its 
legs  may  soon  become  misshapen  if  walking  is  allowed  too 
early.  In  childhood,  the  bones  still  contain  a  larger  percentage 
of  animal  matter  than  in  more  advanced  life,  and  are  therefore 
more  liable  to  bend  than  to  break  ;  while  in  old  age,  they  con- 
tain a  greater  percentage  of  mineral  matter,  and  are  brittle  and 
easily  broken. 

Experiment  3.  To  show  the  mineral  matter  in  bone.  Weigh  a  large 
soup  bone ;  put  it  on  a  hot,  clear  fire  until  it  is  at  a  red  heat.  At  first  it 
becomes  black  from  the  carbon  of  its  organic  matter,  but  at 
last  it  turns  white.  Let  it  cool  and  weigh  again.  The  animal 
matter  has  been  burnt  out,  leaving  the  mineral  or  earthy 
part,  a  white,  brittle  substance  of  exactly  the  same  shape,  but 
weighing  only  about  two-thirds  as  much  as  the  bone  originally 
weighed. 

Experiment  4.  To  show  the  animal  matter  in  bone.  Add 
a  teaspoonful  of  muriatic  acid  to  a  pint  of  water,  and  place  the 
mixture  in  a  shallow  earthen  dish.  Scrape  and  clean  a 
chicken's  leg  bone,  part  of  a  sheep's  rib,  or  any  other  small, 
thin  bone.  Soak  the  bone  in  the  acid  mixture  for  a  few  days. 
The  earthy  or  mineral  matter  is  slowly  dissolved,  and  the 
bone,  although  retaining  its  original  form,  loses  its  rigidity, 
and  becomes  pliable,  and  so  soft  as  to  be  readily  cut.  If  the 
experiment  be  carefully  performed,  a  long,  thin  bone  may  even 
be  tied  into  a  knot. 

29.  Physical  Properties  of  Bone.  If  we  take  a  leg 
bone  of  a  sheep,  or  a  large  end  of  beef  shin  bone,  and 
saw  it  lengthwise  in  halves,  we  see  two  distinct  structures. 
There  is  a  hard  and  compact  tissue,  like  ivory,  forming  the 
outside  shell,  and  a  spongy  tissue  inside  having  the  appearance 
of  a  beautiful  lattice  work.  Hence  this  is  called  cancellous 
tissue,  and  the  gradual  transition  from  one  to  the  other  is 
apparent. 


24  PRACTICAL    PHYSIOLOGY. 


It  will  also  be  seen  that  the  shaft  is  a  hollow 
cylinder,  formed  of  compact  tissue,  enclosing 
a  cavity  called  the  medullary  canal,  which  is 
filled  with  a  pulpy,  yellow  fat  called  marrow. 
The  marrow  is  richly  supplied  with  blood- 
vessels, which  enter  the  cavity  through  small 
openings  in  the  compact  tissue.  In  fact,  all 
over  the  surface  of  bone  are  minute  canals 
leading  into  the  substance.  One  of  these, 
especially  constant  and  large  in  many  bones, 
is  called  the  nutrient  foramen,  and  transmits 
an  artery  to  nourish  the  bone. 

At  the  ends  of  a  long  bone,  where  it  ex- 
pands, there  is  no  medullary  canal,  and  the 
bony  tissue  is  spongy,  with  only  a  thin  layer 
of  dense  bone  around  it.  In  flat  bones  we 
find  two  layers  or  plates  of  compact  tissue  at 
the  surface,  and  a  spongy  tissue  between. 
Short  and  irregular  bones  have  no  medullary 
canal,  only  a  thin  shell  of  dense  bone  filled 
with  cancellous  tissue. 


h      '  h          Experiment  5.     Obtain  a  part  of  a  beef  shin  bone, 

'      '          ,.  or  a  portion  of  a  sheep's  or  calf's  leg,  including  if  con- 

lenethwise    (Show-  venient  tne  knee  joint.     Have  the  bone  sawed  in  two, 

ing  arrangement  of  lengthwise,  keeping  the  marrow  in  place.     Boil,  scrape, 

compact    and  can-  and  carefully  clean  one  half.     Note  the  compact  and 

cellous  tissue.)  spongy  parts,  shaft,  etc. 

Experiment  6.  Trim  off  the  flesh  from  the  second  half.  Note  the 
pinkish  white  appearance  of  the  bone,  the  marrow,  and  the  tiny  specks  of 
blood,  etc.  Knead  a  small  piece  of  the  marrow  in  the  palm ;  note  the 
oily  appearance.  Convert  some  marrow  into  a  liquid  by  heating.  Con- 
trast this  fresh  bone  with  an  old  dry  one,  as  found  in  the  fields.  Fresh 
bones  should  be  kept  in  a  cool  place,  carefully  wrapped  in  a  damp  cloth, 
while  waiting  for  class  use. 


THE    BONES.  25 

A  fresh  or  living  bone  is  covered  with  a  delicate,  tough, 
fibrous  membrane,  called  the  periosteum.  It  adheres  very 
closely  to  the  bone,  and  covers  every  part  except  at  the  joints 
and  where  it  is  protected  with  cartilage.  The  periosteum  is 
richly  supplied  with  blood-vessels,  and  plays  a  chief  part  in  the 
growth,  formation,  and  repair  of  bone.  If  a  portion  of  the 
periosteum  be  detached  by  injury  or  disease,  there  is  risk  that 
a  layer  of  the  subjacent  bone  will  lose  its  vitality  and  be 
cast  off.1 

30.  Microscopic  Structure  of  Bone.  If  a  very  thin  slice  of 
bone  be  cut  from  the  compact  tissue  and  examined  under 
a  microscope,  numerous  minute  openings  are  seen.  Around 
these  are  arranged  rings  of  bone,  with  little  black  bodies  in 
them,  from  which  radiate  fine,  dark  lines.  These  openings  are 
sections  of  canals  called  Haversian  canals,  after  Havers,  an 
English  physician,  who  first  discovered  them.  The  black  bodies 
are  minute  cavities  called  lacuntz,  while  the  fine  lines  are  very 
minute  canals,  canaliculi,  which  connect  the  lacunae  and  the 
Haversian  canals.  These  Haversian  canals  are  supplied  with 
tiny  blood-vessels,  while  the  lacunae  contain  bone  cells.  Very 
fine  branches  from  these  cells  pass  into  the  canaliculi.  The 
Haversian  canals  run  lengthwise  of  the  bone ;  hence  if  the 
bone  be  divided  longitudinally  these  canals  will  be  opened 
along  their  length  (Fig.  13). 

Thus  bones  are  not  dry,  lifeless  substances,  but  are  the 
very  type  of  activity  and  change.  In  life  they  are  richly  sup- 

1  The  periosteum  is  often  of  great  practical  importance  to  the  surgeon.  Instances 
are  on  record  where  bones  have  been  removed,  leaving  the  periosteum,  within  which 
the  entire  bone  has  grown  again.  The  importance  of  this  remarkable  tissue  is  still 
farther  illustrated  by  experiments  upon  the  transplantation  of  this  membrane  in  the 
different  tissues  of  living  animals,  which  has  been  followed  by  the  formation  of  bone 
in  these  situations.  Some  years  ago  a  famous  surgeon  in  New  York  removed  the 
whole  lower  jawbone  from  a  young  woman,  leaving  the  periosteum  and  even  retaining 
in  position  the  teeth  by  a  special  apparatus.  The  entire  jawbone  grew  again,  and 
the  teeth  resumed  their  original  places  as  it  grew. 


26 


PRACTICAL    PHYSIOLOGY. 


plied  with  blood  from  the  nutrient  artery  and  from  the  peri- 
osteum, by  an  endless  network  of  nourishing  canals  throughout 
their  whole  structure.  Bone  has,  therefore,  like  all  other  living 
structures,  a  self -formative  power,  and  draws  from  the  blood 
the  materials  for  its  own  nutrition. 


FIG.  13. 

A,  longitudinal  section  of  bone,  by  which  the  Haversian  canals  are  seen  branching 
and  communicating  with  one  another ;  B,  cross  section  of  a  very  thin  slice  of 
bone,  magnified  about  300  diameters  —  little  openings  (Haversian  canals)  are 
seen,  and  around  them  are  ranged  rings  of  bones  with  little  black  bodies  (lacunas), 
from  which  branch  out  fine  dark  lines  (canaliculi)  ;  C,  a  bone  cell,  highly  magni- 
fied, lying  in  lacuna. 


THE  BONES  OF  THE  HEAD. 

31.  The  Head,  or  Skull.  The  bones  of  the  skeleton,  the 
bony  framework  of  our  bodies,  may  be  divided  into  those  of 
the  head,  the  trunk,  and  the  limbs. 

The  bones  of  the  head  are  described  in  two  parts,  —  those 
of  the  cranium,  or  brain-case,  and  those  of  the  face.  Taken 
together,  they  form  the  skull.  The  head  is  usually  said  to  con- 
tain 22  bones,  of  which  8  belong  to  the  cranium  and  14  to  the 
face.  In  early  childhood,  the  bones  of  the  head  are  separate 
to  allow  the  brain  to  expand  ;  but  as  we  grow  older  they  gradu- 
ally unite,  the  better  to  protect  the  delicate  brain  tissue. 


THE    BONES.  2/ 

32.  The  Cranium.  The  cranium  is  a  dome-like  structure, 
made  up  in  the  adult  of  8  distinct  bones  firmly  locked  together. 
These  bones  are  : 

One  Frontal,  One  Occipital, 

Two  Parietal,  One  Sphenoid, 

Two  Temporal,  One  Ethmoid. 

The  frontal  bone  forms  the  forehead  and  front  of  the  head. 
It  is  united  with  the  two  parietal  bones  behind,  and  extends 
over  the  forehead  to  make  the  roofs  of  the  sockets  of  the  eyes. 
It  is  this  bone  which,  in  many  races  of  man,  gives  a  dignity  of 
person  and  a  beauty  of  form  seen  in  no  other  animal. 

The  parietal  bones  form  the  sides  and  roof  of  the  skull. 
They  are  bounded  anteriorly  by  the  frontal  bone,  posteriorly 
by  the  occipital,  and  laterally  by  the  temporal  and  sphenoid 
bones.  The  two  bones  make  a  beautiful  arch  to  aid  in  the 
protection  of  the  brain. 

The  temporal  bones,  forming  the  temples  on  either  side, 
are  attached  to  the  sphenoid  bone  in  front,  the  parietals  above, 
and  the  occipital  behind.  In  each  temporal  bone  is  the  cavity 
containing  the  organs  of  hearing.  These  bones  are  so  called 
because  the  hair  usually  first  turns  gray  over  them. 

The  occipital  bone  forms  the  lower  part  of  the  base  of  the 
skull,  as  well  as  the  back  of  the  head.  It  is  a  broad,  curved 
bone,  and  rests  on  the  topmost  vertebra  (atlas)  of  the  back- 
bone ;  its  lower  part  is  pierced  by  a  large  oval  opening  called 
the  foramen  magnum,  through  which  the  spinal  cord  passes 
from  the  brain  (Fig.  15). 

The  sphenoid  bone  is  in  front  of  the  occipital,  forming  a 
part  of  the  base  of  the  skull.  It  is  wedged  between  the  bones 
of  the  face  and  those  of  the  cranium,  and  locks  together  four- 
teen different  bones.  It  bears  a  remarkable  resemblance  to  a 
bat  with  extended  wings,  and  forms  a  series  of  girders  to  the 
arches  of  the  cranium. 


28 


PRACTICAL    PHYSIOLOGY. 


The  ethmoid  bone  is  situated  between  the  bones  of  the 
cranium  and  those  of  the  face,  just  at  the  root  of  the  nose. 
It  forms  a  part  of  the  floor  of  the  cranium.  It  is  a  delicate, 
spongy  bone,  and  is  so  called  because  it  is  perforated  with 


FIG.  14.  — The  Skull. 


numerous  holes  like  a  sieve,  through  which  the  nerves  of  smell 
pass  from  the  brain  to  the  nose. 

33.  The  Face.  The  bones  of  the  face  serve,  to  a  marked 
extent,  in  giving  form  and  expression  to  the  human  counte- 
nance. Upon  these  bones  depend,  in  a  measure,  the  build  of 
the  forehead,  the  shape  of  the  chin,  the  size  of  the  eyes,  the 


THE    BONES.  2Q 

prominence  of  the  cheeks,  the  contour  of  the  nose,  and  other 
marks  which  are  reflected  in  the  beauty  or  ugliness  of  the  face. 

The  face  is  made  up  of  fourteen  bones  which,  with  the 
exception  of  the  lower  jaw,  are,  like  those  of  the  cranium, 
closely  interlocked  with  each  other.  By  this  union  these  bones 
help  form  a  number  of  cavities  which  contain  most  important 
and  vital  organs.  The  two  deep,  cup-like  sockets,  called  the 
orbits,  contain  the  organs  of  sight.  In  the  cavities  of  the  nose 
is  located  the  sense  of  smell,  while  the  buccal  cavity,  or  mouth, 
is  the  site  of  the  sense  of  taste,  and  plays  besides  an  important 
part  in  the  first  act  of  digestion  and  in  the  function  of  speech. 

The  bones  of  the  face  are : 

Two  Superior  Maxillary,  Two  Palate, 

Two  Malar,  Two  Turbinated, 

Two  Nasal,  One  Vomer, 

Two  Lachrymal,  One  Lower  Maxillary. 

34.  Bones  of  the  Face.  The  superior  maxillary  or  upper 
jawbones  form  a  part  of  the  roof  of  the  mouth  and  the  entire 
floor  of  the  orbits.  In  them  is  fixed  the  upper  set  of  teeth. 

The  malar  or  cheek  bones  are  joined  to  the  upper  jaw- 
bones, and  help  form  the  sockets  of  the  eyes.  They  send  an 
arch  backwards  to  join  the  temporal  bones.  These  bones  are 
remarkably  thick  and  strong,  and  are  specially  adapted  to 
resist  the  injury  to  which  this  part  of  the  face  is  exposed. 

The  nasal  or  nose  bones  are  two  very  small  bones  between 
the  eye  sockets,  which  form  the  bridge  of  the  nose.  Very  near 
these  bones  are  the  two  small  lachrymal  bones.  These  are 
placed  in  the  inner  angles  of  the  orbit,  and  in  them  are  grooves 
in  which  lie  the  ducts  through  which  the  tears  flow  from  the 
eyes  to  the  nose. 

The  palate  bones  are  behind  those  of  the  upper  jaw  and  with 
them  form  the  bony  part  of  the  roof  of  the  mouth.  The  in- 
ferior turbinated  are  spongy,  scroll-like  bones,  which  curve 


3O  PRACTICAL    PHYSIOLOGY. 

about  within  the  nasal  cavities  so  as  to  increase  the  surface  of 

the  air  passages  of  the  nose. 

The  vomer  serves  as  a  thin  and  delicate  partition  between 

the  two  cavities  of  the  nose. 
It  is  so  named  from  its  resem- 
blance to  a  ploughshare. 

The  longest  bone  in  the  face 
is  the  inferior  maxillary,  or 
lower  jaw.  It  has  a  horseshoe 
shape,  and  supports  the  lower 
set  of  teeth.  It  is  the  only 
movable  bone  of  the  head,  hav- 
ing a  vertical  and  lateral  motion 
by  means  of  a  hinge  joint  with 
a  part  of  the  temporal  bone. 

35.  Sutures  of  the  Skull.  Be- 
fore leaving  the  head  we  must 
notice  the  peculiar  and  admirable 

manner  in  which  the  edges  of  the 
FIG.  15.  —  The  Base  of  the  Skull.         .  ,     . 

bones  of  the   outer   shell    of   the 

A,  palate  process  of  upper  jawbone.     B,  zy-      .  .    . 

goma,  forming  zygomatic  arch.    C,condyle   sku11    are    JOmed    together.       These 

for  forming  articulation  with  atlas.   D,  fo-  edges  of  the  bones*  resemble  the 

ramen  magnum.     E,  occipital  bone.  ^th  of  a  saw.      In  adult  life  these 

tooth-like  edges  fit  into  each  other  and  grow  together,  suggesting  the 
dovetailed  joints  used  by  the  cabinet-maker.  When  united  these 
serrated  edges  look  almost  as  if  sewed  together  ;  hence  their  name, 
sutures.  This  manner  of  union  gives  unity  and  strength  to  the  skull. 
In  infants,  the  corners  of  the  parietal  bones  do  not  yet  meet,  and 
the  throbbing  of  the  brain  may  be  seen  and  felt  under  these  "  soft 
spots,"  or  fontanelles,  as  they  are  called.  Hence  a  slight  blow  to  a 
babe's  head  may  cause  serious  injury  to  the  brain  (Fig.  14). 

THE    BONES    OF   THE   TRUNK. 

36.    The  Trunk.     The  trunk  is  that  central  part  of  the  body 
which  supports    the  head  and  the   upper    pair    of   limbs.     It 


THE    BONES.  31 

divides  itself  into  an  upper  cavity,  the  thorax,  or  chest ;  and 
a  lower  cavity,  the  abdomen.  These  two  cavities  are  separated 
by  a  movable,  muscular  partition  called  the  diaphragm,  or 
midriff  (Figs.  9  and  49). 

The  bones  of  the  trunk  are  variously  related  to  each  other, 
and  some  of  them  become  united  during  adult  life  into  bony 
masses  which  at  earlier  periods  are  quite  distinct.  For  ex- 
ample, the  sacrum  is  in  early  life  made  up  of  five  distinct 
bones  which  later  unite  into  one. 

The  upper  cavity,  or  chest,  is  a  bony  enclosure  formed  by  the 
breastbone,  the  ribs,  and  the  spine.  It  contains  the  heart  and 
the  lungs  (Fig.  86). 

The  lower  cavity,  or  abdomen,  holds  the  stomach,  liver, 
intestines,  spleen,  kidneys,  and  some  other  organs  (Fig.  59). 

The  bones  of  the  trunk  may  be  subdivided  into  those  of  the 
spine,  the  ribs,  and  the  hips. 

The  trunk  includes  54  bones  usually  thus  arranged : 


I.  Spinal  Column,  26  bones: 


7  Cervical  Vertebrae. 
12  Dorsal  Vertebras. 
5  Lumbar  Vertebrae. 


i  Sacrum, 
i  Coccyx. 

{14  True  Ribs. 
6  False  Ribs. 
4  Floating  Ribs. 

III.  Sternum. 

IV.  Two  Hip  Bones. 
V.  Hyoid  Bone. 

37.  The  Spinal  Column.  The  spinal  column,  or  back- 
bone, is  a  marvelous  piece  of  mechanism,  combining  offices 
which  nothing  short  of  perfection  in  adaptation  and  arrange- 
ment could  enable  it  to  perform.  It  is  the  central  structure  to 
which  all  the  other  parts  of  the  skeleton  are  adapted.  It  con- 


PRACTICAL    PHYSIOLOGY. 


sists  of  numerous  separate  bones,  called  vertebrae.  The  seven 
upper  ones  belong  to  the  neck,  and 
are  called  cervical  vertebrae.  The 
next  twelve  are  the  dorsal  vertebrae ; 
these  belong  to  the  back  and  support 
the  ribs.  The  remaining  five  belong 
to  the  loins,  and  are  called  lumbar 
vertebrae.  On  looking  at  the  diagram 
of  the  backbone  (Fig.  9)  it  will  be  seen 
that  the  vertebrae  increase  in  size  and 
strength  downward,  because  of  the 
greater  burden  they  have  to  bear,  thus 
clearly  indicating  that  an  erect  posi- 
tion is  the  one  natural  to  man. 

This  column  supports  the  head,  en- 
closes and  protects  the  spinal  cord, 
and  forms  the  basis  for  the  attachment 
of  many  muscles,  especially  those 
which  maintain  the  body  in  an  erect 
position.  Each  vertebra  has  an  open- 
ing through  its  center,  and  the  separ- 
ate bones  so  rest,  one  upon  another, 
that  these  openings  form  a  continuous 
canal  from  the  head  to  the  lower  part 
of  the  spine.  The  great  nerve,  known 
as  the  spinal  cord,  extends  from  the 
cranium  through  the  entire  length  of 
this  canal.  All  along  the  spinal  col- 
umn, and  between  each  two  adjoining 
bones,  are  openings  on  each  side, 
through  which  nerves  pass  out  to  be 
distributed  to  various  parts  of  the  body. 
Between  the  vertebrae  are  pads  or 
cushions  of  cartilage.  These  act  as 


COCCYX 


FIG  16.  — The  Spinal 
Column. 


THE    BONES.  33 

"  buffers,"  and  serve  to  give  the  spine  strength  and  elasticity 
and  to  prevent  friction  of  one  bone  on  another.  Each  vertebra 
consists  of  a  body,  the  solid  central  portion,  and  a  number  of 
projections  called  processes.  Those  which  spring  from  the 
posterior  of  each  arch  are  the  spinous  processes.  In  the  dorsal 
region  they  are  plainly  seen  and  felt  in  thin  persons. 

The  bones  of  the  spinal  column  are  arranged  in  three  slight 
and  graceful  curves.  These  curves  not  only  give  beauty  and 
strength  to  the  bony  framework  of  the  body,  but  also  assist  in 
the  formation  of  cavities  for  important  internal  organs.  This 
arrangement  of  elastic  pads  between  the  vertebrae  supplies 
the  spine  with  so  many  elastic  springs,  which  serve  to  break 
the  effect  of  shock  to  the  brain  and  the  spinal  cord  from  any 
sudden  jar  or  injury. 

The  spinal  column  rests  on  a  strong  three-sided  bone  called 
the  sacrum,  or  sacred-bone,  which  is  wedged  in  between  the 
hip  bones  and  forms  the  keystone  of  the  pelvis.  Joined  to  the 
lower  end  of  the  sacrum  is  the  coccyx,  or  cuckoo-bone,  a  taper- 
ing series  of  little  bones. 

Experiment  7.  Run  the  tips  of  the  fingers  briskly  down  the  backbone, 
and  the  spines  of  the  vertebrae  will  be  tipped  with  red  so  that  they  can  be 
readily  counted.  Have  the  model  lean  forward  with  the  arms  folded 
across  the  chest ;  this  will  make  the  spines  of  the  vertebrae  more 
prominent. 

Experiment  8.  To  illustrate  the  movement  of  torsion  in  the  spine,  or  its 
rotation  round  its  own  axis.  Sit  upright,  with  the  back  and  shoulders  well 
applied  against  the  back  of  a  chair.  Note  that  the  head  and  neck  can  be 
turned  as  far  as  60°  or  70°.  Now  bend  forwards,  so  as  to  let  the  dorsal 
and  lumbar  vertebras  come  into  play,  and  the  head  can  be  turned  30°  more. 

Experiment  9.  To  show  how  the  spinal  vertebra  make  a  firm  but  flexi- 
ble column.  Take  24  hard  rubber  overcoat  buttons,  or  the  same  number 
of  two-cent  pieces,  and  pile  them  on  top  of  each  other.  A  thin  layer  of 
soft  putty  may  be  put  between  the  coins  to  represent  the  pads  of  cartilage 
between  the  vertebrae.  The  most  striking  features  of  the  spinal  column 
may  be  illustrated  by  this  simple  apparatus. 


34  PRACTICAL    PHYSIOLOGY. 

38.  How  the  Head  and  Spine  are  Joined  together.      The   head 
rests  upon  the  spinal  column  in  a  manner  worthy  of  special  notice. 
This  consists  in  the  peculiar  structure  of  the  first  two  cervical  verte- 
brae, known  as  the  axis  and  atlas.      The  atlas  is  named  after  the 
fabled  giant  who  supported  the  earth  on  his  shoulders.     This  verte- 
bra consists  of  a  ring  of  bone,  having  two  cup-like  sockets  into  which 
fit  two  bony  projections  arising  on  either  side  of  the  great  opening 
(foramen    magnum)  in  the  occipital   bone.     The  hinge  joint  thus 
formed  allows  the  head  to  nod  forward,  while  ligaments  prevent  it 
from  moving  too  far. 

On  the  upper  surface  of  the  axis,  the  second  vertebra,  is  a  peg  or 
process,  called  the  odontoid  process  from  its  resemblance  to  a  tooth. 
This  peg  forms  a  pivot  upon  which  the  head  with  the  atlas  turns.  It 
is  held  in  its  place  against  the  front  inner  surface  of  the  atlas  by  a 
band  of  strong  ligaments,  which  also  prevents  it  from  pressing  on  the 
delicate  spinal  cord.  Thus,  when  we  turn  the  head  to  the  right 
or  left,  the  skull  and  the  atlas  move  together,  both  rotating  on  the 
odontoid  process  of  the  axis. 

39.  The  Ribs  and  Sternum.     The  barrel-shaped  framework 
of  the  chest  is  in  part  composed  of  long,  slender,  curved  bones 
called  ribs.     There  are  twelve  ribs  on  each  side,  which  enclose 
and  strengthen  the  chest ;   they  somewhat  resemble  the  hoops 
of  a  barrel.     They  are  connected  in  pairs  with  the  dorsal  verte- 
brae behind. 

The  first  seven  pairs,  counting  from  the  neck,  are  called  the 
true  ribs,  and  are  joined  by  their  own  special  cartilages  directly  to 
the  breastbone.  The  five  lower  pairs,  called  \hzfalse  ribs,  are 
not  directly  joined  to  the  breastbone,  but  are  connected,  with 
the  exception  of  the  last  two,  with  each  other  and  with  the 
last  true  ribs  by  cartilages.  These  elastic  cartilages  enable 
the  chest  to  bear  great  blows  with  impunity.  A  blow  on  the 
sternum  is  distributed  over  fourteen  elastic  arches.  The 
lowest  two  pairs  of  false  ribs,  are  not  joined  even  by  cartilages, 
but  are  quite  free  in  front,  and  for  this  reason  are  called  float- 
ing ribs. 


THE    BONES. 


35 


The  ribs  are  not  horizontal,  but  slope  downwards  from  the 
backbone,  so  that  when  raised  or  depressed  by  the  strong  inter- 
costal muscles,  the  size  of  the  chest  is  alternately  increased  or 
diminished.  This  movement  of  the  ribs  is  of  the  utmost 
importance  in  breathing  (Fig.  91). 

The    sternum,  or  breastbone,  is  a  long,  flat,  narrow  bone 
forming  the  middle  front  wall  of  the  chest.     It  is  connected 
with  the  ribs  and  with  the 
collar  bones.     In  shape  it 
somewhat    resembles   an 
ancient  dagger. 

40.   The  Hip  Bones. 

Four  immovable  bones  are 
joined  together  so  as  to 
form  at  the  lower  ex- 
tremity of  the  trunk  a 
basin-like  cavity  called  the 
pelvis.  These  four  bones 
are  the  sacrum  and  the 
coccyx,  which  have  been 
described,  and  the  two  hip 
bones. 

The  hip  bones  are  large, 
irregularly    shaped    bones, 

very  firm  and  strong,  and  are  sometimes  called  the  haunch 
bones  or  ossa  innominata  (nameless  bones).  They  are  united 
to  the  sacrum  behind  and  joined  to  each  other  in  front.  On 
the  outer  side  of  each  hip  bone  is  a  deep  cup,  or  socket, 
called  the  acetabulum,  resembling  an  ancient  vinegar  cup,  into 
which  fits  the  rounded  head  of  the  thigh  bone.  The  bones  of 
the  pelvis  are  supported  like  a  bridge  on  the  legs  as  pillars, 
and  they  in  turn  contain  the  internal  organs  in  the  lower  part 
of  the  trunk. 


FIG.  17.  —  Thorax.     (Anterior  view.) 


36  PRACTICAL    PHYSIOLOGY. 

41.  The  Hyoid  Bone.  Under  the  lower  jaw  is  a  little  horseshoe- 
shaped  bone  called  the  hyoid  bone,  because  it  is  shaped  like  the  Greek 
letter  upsilon  (T).  The  root  of  the  tongue  is  fastened  to  its  bend, 
and  the  larynx  is  hung  from  it  as  from  a  hook.  When  the  neck  is  in 
its  natural  position  this  bone  can  be  plainly  felt  on  a  level  with  the 
lower  jaw  and  about  one  inch  and  a  half  behind  it.  It  serves  to 
keep  open  the  top  of  the  larynx  and  for  the  attachment  of  the  muscles 
which  move  the  tongue.  (See  Fig.  46.)  The  hyoid  bone,  like  the 
knee-pan,  is  not  connected  with  any  other  bone. 


THE    BONES    OF   THE    UPPER   LIMBS. 

42.  The  Upper  Limbs.     Each  of  the  upper  limbs  consists 
of  the  upper  arm,  the  forearm,  and  the  hand.     These  bones 
are  classified  as  follows : 

f  Scapula,  or  shoulder-blade, 
Upper  Arm  :  -^   Clavicle,  or  collar  bone, 
^  Humerus,  or  arm  bone, 

Forearm:/111118' 
^  Radius, 

{&  Carpal  or  wrist  bones, 
5  Metacarpal  bones, 
14  Phalanges,  or  finger  bones, 

making  32  bones  in  all. 

43.  The  Upper  Arm.     The  two  bones  of  the  shoulder,  the 
scapula  and  the  clavicle,  serve  in  man  to  attach  the  arm  to  the 
trunk.      The  scapula,   or  shoulder-blade,  is  a  flat,  triangular 
bone,  placed    point  downwards,  and  lying  on  the  upper  and 
back  part  of  the  chest,  over  the  ribs.     It  consists  of  a  broad, 
flat  portion  and  a  prominent  ridge  or  spine.     At  its  outer  angle 
it  has  a  shallow  cup  known  as  the  glenoid  cavity.     Into  this 
socket  fits  the  rounded  head  of  the  humerus.     The  shoulder- 
blade  is  attached  to  the  trunk  chiefly  by  muscles,  and  is  capable 
of  extensive  motion. 


THE    BONES. 


37 


The  clavicle,  or  collar  bone,  is  a  slender  bone  with  a  double 
curve  like  an  italic  f,  and  extends  from  the  outer  angle  of  the 
shoulder-blade  to  the  top  of  the  breastbone.  It  thus  serves  like 


>'(> 


the 
key- 
stone 
of    an 
arch    to 
hold  the  shoul- 
der-blade   firmly 
in  its  place,  but  its 
chief  use  is  to  keep  the 
shoulders  wide  apart,  that 
the  arm  may  enjoy  a  freer 
range  of  motion.    This  bone 
is  often  broken  J)y  falls  upon 
the  shoulder  or  arm. 

The  humerus  is  the  strong- 
est bone  of  the  upper  extrem- 
ity.    As  already  mentioned,  its 
rounded  head  fits  into  the  socket 
of  the  shoulder-blade,  forming  a 
ball-and-socket  joint,  which  permits 
great  freedom  of  motion.    The  shoul- 
der   joint    resembles    what    mechanics 
call  a  universal  joint,  for  there  is  no  part  of 
the  body  which  cannot  be  touched  by  the  hand. 

When  the  shoulder  is  dislocated  the  head 
of  the  humerus  has  been  forced  out  of  its 
socket.     The  lower  end  of  the  bone  is  grooved  to  help  form  a 
hinge  joint  at  the  elbow  with  the  bones  of  the  forearm  (Fig.  27). 


FIG.  1 8. 

Left  Scapula,  or 
Shoulder-Blade. 


PRACTICAL    PHYSIOLOGY. 


44.  The  Forearm.  The  forearm  contains  two  long  bones, 
the  ulna  and  the  radius.  The  ulna,  so  called  because  it  forms 
the  elbow,  is  the  longer  and  larger  bone  of  the  forearm,  and  is 
on  the  same  side  as  the  little  finger.  It  is 
connected  with  the  humerus  by  a  hinge  joint 
at  the  elbow.  It  is  prevented  from  moving 
too  far  back  by  a  hook-like  projection  called 
the  olecranon  process,  which  makes  the  sharp 
point  of  the  elbow. 

The  radius  is  the  shorter  of  the  two  bones 
of  the  forearm,  and  is  on  the  same  side  as  the 
thumb.  Its  slender,  upper  end  articulates 
with  the  ulna  and  humerus  ;  its  lower  end  is 
enlarged  and  gives  attachment  in  part  to  the 
bones  of  the  wrist.  This  bone  radiates  or 
turns  on  the  ulna,  carrying  the  hand  with  it. 

Experiment  10.  Rest  the  forearm  on  a  table,  with 
the  palm  up  (an  attitude  called  supination).  The 
radius  is  on  the  outer  side  and  parallel  with  the  ulna. 
If  now,  without  moving  the  elbow,  we  turn  the  hand 
(pronation),  as  if  to  pick  up  something  from  the  table, 
the  radius  may  be  seen  and  felt  crossing  over  the  ulna, 
while  the  latter  has  not  moved. 


FIG.  19.— Left  Cla- 
vicle, or  Collar 
Bone.  (Anterior 
surface.) 


45.  The  Hand.  The  hand  is  the  executive 
or  essential  part  of  the  upper  limb.  Without 
it  the  arm  would  be  almost  useless.  It  con- 
sists of  27  separate  bones,  and  is  divided  into  three  parts,  the 
wrist,  the  palm,  and  the  fingers. 

The  carpus,  or  wrist,  includes  8  short  bones,  arranged  in  two 
rows  of  four  each,  so  as  to  form  a  broad  support  for  the  hand. 
These  bones  are  closely  packed,  and  tightly  bound  with  liga- 
ments which  admit  of  ample  flexibility.  Thus  the  wrist  is  much 
less  liable  to  be  broken  than  if  it  were  to  consist  of  a  single 
bone,  while  the  elasticity  from  having  the  eight  bones  movable 


THE    BONES. 


39 


FIG.  20.  —  Left  Humerus.  FIG.  21.  —  Left  Radius  and  Ulna. 


4O  .         PRACTICAL    PHYSIOLOGY. 

on  each  other,  neutralizes,  to  a  great  extent,  a  shock  caused  by 
falling  on  the  hands.  Although  each  of  the  wrist  bones  has  a 
very  limited  mobility  in  relation  to  its  neighbors,  their  combi- 
nation gives  the  hand  that  freedom  of  action  upon  the  wrist, 
which  is  manifest  in  countless  examples  of  the  most  accurate 
and  delicate  manipulation. 

The  metacarpal  bones  are  the  five  long  bones  of  the  back 
of  the  hand.  They  are  attached  to  the  wrist  and  to  the  finger 
bones,  and  may  be  easily  felt  by  pressing  the  fingers  of  one 
hand  over  the  back  of  the  other.  The  metacarpal  bones  of 
the  fingers  have  little  freedom  of  movement,  while  the  thumb, 
unlike  the  others,  is  freely  movable.  We  are  thus  enabled  to 
bring  the  thumb  in  opposition  to  each  of  the  fingers,  a  matter 
of  the  highest  importance  in  manipulation.  For  this  reason 
the  loss  of  the  thumb  disables  the  hand  far  more  than  the 
loss  of  either  of  the  fingers.  This  very  significant  opposition 
of  the  thumb  to  the  fingers,  furnishing  the  complete  grasp  by 
the  hand,  is  characteristic  of  the  human  race,  and  is  wanting  in 
the  hand  of  the  ape,  chimpanzee,  and  ourang-outang. 

The  phalanges,  or  finger  bones,  are  the  fourteen  small  bones 
arranged  in  three  rows  to  form  the  fingers.  Each  finger  has 
three  bones  ;  each  thumb,  two. 

The  large  number  of  bones  in  the  hand  not  only  affords 
every  variety  of  movement,  but  offers  great  resistance  to  blows 
or  shocks.  These  bones  are  united  by  strong  but  flexible  liga- 
ments. The  hand  is  thus  given  strength  and  flexibility,  and 
enabled  to  accomplish  the  countless  movements  so  necessary 
to  our  well-being. 

In  brief,  the  hand  is  a  marvel  of  precise  and  adapted  mechan- 
ism, capable  not  only  of  performing  every  variety  of  work  and 
of  expressing  many  emotions  of  the  mind,  but  of  executing  its 
orders  with  inconceivable  rapidity. 


THE    BONES. 


THE  BONES  OF  THE  LOWER  LIMBS. 

46.     The    Lower    Limbs.      The 

general  structure  and  number  of  the 
bones  of  the  lower  limbs  bear  a  strik- 
ing similarity  to  those  of  the  upper 
limbs.  Thus  the  leg,  like  the  arm,  is 
arranged  in  three  parts,  the  thigh, 
the  lower  leg,  and  the  foot.  The 
thigh  bone  corresponds  to  the  hume- 
rus  ;  the  tibia  and  fibula  to  the  ulna 
and  radius  ;  the  ankle  to  the  wrist ; 
and  the  metatarsus  and  the  phalanges 
of  the  foot,  to  the  metacarpus  and  the 
phalanges  of  the  hand. 

The  bones  of  the  lower  limbs  may 
be  thus  arranged : 

Thigh  :  Femur,  or  thigh  bone, 

(  Patella,  or  knee-cap, 
Lower  Leg :  J  Tibia,  or  shin  bone, 

t  Fibula,  or  splint  bone, 

7  Tarsal  orankle  bones, 
5  Metatarsal  or  instep 
Foot :  \  bones, 

I  14  Phalanges,     or     toe 

L  bones, 

making  30  bones  in  all. 

47.  The  Thigh.  The  longest  and 
strongest  of  all  the  bones  is  the 
femur,  or  thigh  bone.  Its  upper 
end  has  a  rounded  head  which  fits 
into  the  acetabulum,  or  the  deep  cup- 
like  cavity  of  the  hip  bone,  forming 


FIG.  22.  —  Right  Femur,  or 
Thigh  Bone. 


42  PRACTICAL    PHYSIOLOGY. 

a  perfect  ball-and-socket  joint.  When  covered  with  cartilage, 
the  ball  fits  so  accurately  into  its  socket  that  it  may  be  retained 
by  atmospheric  pressure  alone  (sec.  50). 

The  shaft  of  the  femur  is  strong,  and  is  ridged  and  roughened 
in  places  for  the  attachment  of  the  muscles.  Its  lower  end  is 
broad  and  irregularly  shaped,  having  two  prominences  called 
condyles,  separated  by  a  groove,  the  whole  fitted  for  forming  a 
hinge  joint  with  the  bones  of  the  lower  leg  and  the  knee-cap. 

48.  The  Lower  Leg.     The  lower  leg,  like  the  forearm,  con- 
sists of  two  bones.     The  tibia,  or  shin  bone,  is  the  long  three- 
sided  bone  forming  the  front  of  the  leg. 
The  sharp  edge  of  the  bone  is  easily 
felt  just  under  the  skin.     It  articulates 
with  the  lower  end  of  the  thigh  bone, 
forming  with  it  a  hinge  joint. 

The  fibula,  the  companion  bone  of 
the  tibia,  is  the  long,  slender  bone  on 
the  outer  side  of  the  leg.  It  is  firmly 
fixed  to  the  tibia  at  each  end,  and  is 

FIG.  23.  —  Patella,  or 

Knee-Cap  commonly  spoken  of  as  the  small  bone 

of  the  leg.     Its  lower  end  forms  the 

outer  projection  of  the  ankle.  In  front  of  the  knee  joint, 
embedded  in  a  thick,  strong  tendon,  is  an  irregularly  disk- 
shaped  bone,  the  patella,  or  knee-cap.  It  increases  the  lever- 
age of  important  muscles,  and  protects  the  front  of  the  knee 
joint,  which  is,  from  its  position,  much  exposed  to  injury. 

49.  The  Foot.      The  bones  of  the  foot,  26  in  number,  con- 
sist of  the  tarsal  bones,  the  metatarsal,  and  the  phalanges. 
The  tarsal  bones  are  the  seven   small,  irregular  bones  which 
make  up  the  ankle.     These  bones,  like  those  of  the  wrist,  are 
compactly  arranged,  and  are  held  firmly  in  place  by  ligaments 
which  allow  a  considerable  amount  of  motion. 


THE    BONES. 


43 


One  of  the  ankle  bones,  the  os 
calcis,  projects  prominently  back- 
wards, forming  the  heel.  An  ex- 
tensive surface  is  thus  afforded 
for  the  attachment  of  the  strong 
tendon  of  the  calf  of  the  leg,  called 
the  tendon  of  Achilles.  The  large 
bone  above  the  heel  bone,  the  as- 
tragalus, articulates  with  the  tibia, 
forming  a  hinge  joint,  and  receives 
the  weight  of  the  body. 

The  metatarsal  bones,  corre- 
sponding to  the  metacarpals  of  the 
hand,  are  five  in  number,  and  form 
the  lower  instep. 

The  phalanges  are  the  fourteen 
bones  of  the  toes,  —  three  in  each 
except  the  great  toe,  which,  like 
the  thumb,  has  two.  They  resem- 
ble in  number  and  plan  the  corre- 
sponding bones  in  the  hand.  The 
bones  of  the  foot  form  a  double  arch, 
—  an  arch  from  before  backwards, 
and  an  arch  from  side  to  side. 
The  former  is  supported  behind 
by  the  os  calcis,  and  in  front  by 
the  ends  of  the  metatarsal  bones. 
The  weight  of  the  body  falls  per- 
pendicularly on  the  astragalus, 
which  is  the  key-bone  or  crown 
of  the  arch.  The  bones  of  the 
foot  are  kept  in  place  by  powerful 
ligaments,  combining  great 
strength  with  elasticity. 


FIG.  24.  —  Right  Tibia  and  Fibula. 
(Anterior  surface.) 


44 


PRACTICAL    PHYSIOLOGY. 


FIG.  25.  —  Bones  of  Right  Foot. 
(Dorsal  surface.) 


THE    JOINTS. 

50.  Formation  of  Joints. 

The  various  bones  of  the 
skeleton  are  connected  to- 
gether at  different  parts  of 
their  surfaces  by  joints, 
or  articulations.  Many  dif- 
ferent kinds  of  joints  have 
been  described,  but  the 
same  general  plan  obtains 
for  nearly  all.  They  vary 
according  to  the  kind  and 
the  amount  of  motion. 

The  principal  structures 
which  unite  in  the  forma- 
tion of  a  joint  are :  bone, 
cartilage,  sy  no  vial  mem- 
brane, and  ligaments. 
Bones  make  the  chief  ele- 
ment of  all  the  joints,  and 
their  adjoining  surfaces  are 
shaped  to  meet  the  special 
demands  of  each  joint  (Fig. 
27).  The  joint-end  of  bones 
is  coated  with  a  thin  layer 
of  tough,  elastic  cartilage. 
This  is  also  used  at  the 
edge  of  joint-cavities,  form- 
ing a  ring  to  deepen  them. 
The  rounded  heads  of  bones 
which  move  in  them  are 
thus  more  securely  held  in 
their  sockets. 


THE    BONES. 


45 


Besides  these  structures,  the  muscles  also  help  to  maintain 
the  joint-surfaces  in  proper  relation.  Another  essential  to  the 
action  of  the  joints  is  the  pressure  of  the  outside  air.  This 
may  be  sufficient  to  keep  the  articular  surfaces  in  contact  even 
after  all  the  muscles  are  removed.  Thus  the  hip  joint  is  so 
completely  surrounded  by  ligaments  as  to  be  air-tight ;  and  the 
union  is  very  strong.  But  if  the  ligaments  be  pierced  and  air 
allowed  to  enter  the  joint,  the  union  at  once  becomes  much  less 
close,  and  the  head  of  the  thigh  bone  falls  away  as  far  as  the 
ligaments  will  allow  it. 

51.  Synovial    Membrane.      A    very   delicate    connective 
tissue,  called  the  synovial  membrane,  lines  the  capsules  of  the 
joints,  and  covers  the  ligaments  connected  with  them.  It  secretes 
the  synovia,  or  joint  oil,  a  thick  and  glairy  fluid,  like  the  white 
of  a  raw  egg,  which  thoroughly  lubricates  the  inner  surfaces  of 
the  joints.     Thus  the  friction  and  heat  developed  by  movement 
are  reduced,  and  every  part  of  a  joint  is  enabled  to  act  smoothly. 

52.  Ligaments.     The  bones  are  fastened  together,  held  in 
place,  and  their  movements  controlled,  to  a  certain  extent,  by 
bands  of   various  forms,  called  ligaments.     These  are  com- 
posed mainly  of  bundles  of  white  fibrous  tissue  placed  parallel 
to,  or  closely  interlaced  with,  one  another,  and  present  a  shining, 
silvery  aspect.     They  extend  from  one  of  the  articulating  bones 
to   another,   strongly  supporting  the   joint,   which   they  some- 
times completely  envelope  with  a  kind  of  cap  (Fig.  28).     This 
prevents  the  bones  from  being  easily  dislocated.     It  is  difficult, 
for  instance,  to  separate  the  two  bones  in  a  shoulder  or  leg  of 
mutton,  they  are  so  firmly  held  together  by  tough  ligaments. 

While  ligaments  are  pliable  and  flexible,  permitting  free  move- 
ment, they  are  also  wonderfully  strong  and  inextensible.  A 
bone  may  be  broken,  or  its  end  torn  off,  before  its  ligaments  can 
be  ruptured.  The  wrist  end  of  the  radius,  for  instance,  is  often 
torn  off  by  force  exerted  on  its  ligaments  without  their  rupture. 


46  PRACTICAL    PHYSIOLOGY. 

The  ligaments  are  so  numerous  and  various  and  are  in  some 
parts  so  interwoven  with  each  other,  that  space  does  not  allow 
even  mention  of  those  that  are  important.  At  the  knee  joint, 
for  instance,  there  are  no  less  than  fifteen  distinct  ligaments. 

53.  Imperfect  Joints.  It  is  only  perfect  joints  that  are 
fully  equipped  with  the  structures  just  mentioned.  Some  joints 
lack  one  or  more,  and  are  therefore  called  imperfect  joints. 
Such  joints  allow  little  or  no  motion  and  have 
no  smooth  cartilages  at  their  edges.  Thus,  the 
bones  of  the  skull  are  dovetailed  by  joints  called 
sutures,  which  are  immovable.  The  union  be- 
tween the  vertebrae  affords  a  good  example  of 
.imperfect  joints  which  are  partially  movable. 

54.   Perfect  Joints.    There  are  various  forms 

of  perfect  joints,  according  to  the  nature  and 
FIG.  26.  —  Elastic  J 

Tissue  from  the    amount   of   movement   permitted.       I  hey  are 
Ligaments  about    divided  into  hinge  j  oints,  ball-and-socket  j  oints, 


The  hinge  joints  allow  forward  and  back- 
ward movements  like  a  hinge.  These  joints  are  the  most  numer- 
ous in  the  body,  as  the  elbow,  the  ankle,  and  the  knee  joints. 

In  the  ball-and-socket  joints  —  a  beautiful  contrivance  — 
the  rounded  head  of  one  bone  fits  into  a  socket  in  the  other, 
as  the  hip  joint  and  shoulder  joint.  These  joints  permit  free 
motion  in  almost  every  direction. 

In  the  pivot  joint  a  kind  of  peg  in  one  bone  fits  into  a  notch 
in  another.  The  best  example  of  this  is  the  joint  between  the 
first  and  second  vertebrae  (see  sec.  38).  The  radius  moves 
around  on  the  ulna  by  means  of  a  pivot  joint.  The  radius,  as 
well  as  the  bones  of  the  wrist  and  hand,  turns  around,  thus 
enabling  us  to  turn  the  palm  of  the  hand  upwards  and  down- 
wards. In  many  joints  the  extent  of  motion  amounts  to  only 
a  slight  gliding  between  the  ends  of  the  bones. 


THE    BONES. 


47 


55.  Uses  of  the  Bones.  The  bones  serve  many  important 
and  useful  purposes.  The  skeleton,  a  general  framework, 
affords  protection,  support,  and  leverage  to  the  bodily  tissues. 
Thus,  the  bones  of  the  skull  and  of  the  chest  protect  the  brain, 
the  lungs,  and  the  heart;  the  bones  of  the  legs  support  the 
weight  of  the  body ;  and  the  long  bones 
of  the  limbs  are  levers  to  which  muscles 
are  attached. 

Owing  to  the  various  duties  they  have 
to  perform,  the  bones  are  constructed  in 
many  different  shapes.  Some  are  broad 
and  flat ;  others,  long  and  cylindrical ; 
and  a  large  number  very  irregular  in 
form.  Each  bone  is  not  only  different 
from  all  the  others,  but  is  also  curiously 
adapted  to  its  particular  place  and  use. 

Nothing  could  be  more  admirable 
than  the  mechanism  by  which  each  one 
of  the  bones  is  enabled  to  fulfill  the 
manifold  purposes  for  which  it  was  de- 
signed. We  have  seen  how  the  bones 
of  the  cranium  are  united  by  sutures  in 
a  manner  the  better  to  allow  the  delicate 
brain  to  grow,  and  to  afford  it  protec- 
tion from  violence.  The  arched  ar- 
rangement of  the  bones  of  the  foot  has  several  mechanical 
advantages,  the  most  important  being  that  it  gives  firmness  and 
elasticity  to  the  foot,  which  thus  serves  as  a  support  for  the 
weight  of  the  body,  and  as  the  chief  instrument  of  locomotion. 

The  complicated  organ  of  hearing  is  protected  by  a  winding 
series  of  minute  apartments,  in  the  rock-like  portion  of  the 
temporal  bone.  The  socket  for  the  eye  has  a  jutting  ridge  of 
bone  all  around  it,  to  guard  the  organ  of  vision  against  injury. 
Grooves  and  canals,  formed  in  hard  bone,  lodge  and  protect 


FIG.  27. —  Showing  how  the 
Ends  of  the  Bones  are 
shaped  to  form  the  Elbow 
Joint.  (The  cut  ends  of 
a  few  ligaments  are  seen.) 


48 


PRACTICAL    PHYSIOLOGY. 


minute  nerves  and  tiny  blood-vessels.  The  surfaces  of  bones 
are  often  provided  with  grooves,  sharp  edges,  and  rough  pro- 
jections, for  the  origin  and  insertion  of  muscles. 

56.   The  Bones  in  Infancy  and  Childhood.     The  bones  of 

the  infant,  consisting  almost  wholly  of  cartilage,  are  not  stiff 
and  hard  as  in  after  life,  but  flexible  and  elastic.  As  the 

child  grows,  the  bones  become  more 
solid  and  firmer  from  a  gradually 
increased  deposit  of  lime  salts.  In 
time  they  become  capable  of  sup- 
porting the  body  and  sustaining 
the  action  of  the  muscles.  The 
reason  is  that  well-developed  bones 
would  be  of  no  use  to  a  child  that 
had  not  muscular  strength  to  sup- 
port its  body.  Again,  the  numerous 
falls  and  tumbles  that  the  child  sus- 
tains before  it  is  able  to  walk,  would 
result  in  broken  bones  almost  every 
day  of  its  life.  As  it  is,  young 
children  meet  with  a  great  variety 
of  falls  without  serious  injury. 

But  this  condition  of  things  has 
its  dangers.  The  fact  that  a  child's 
bones  bend  easily,  also  renders 
them  liable  to  permanent  change 
of  shape.  Thus,  children  often  be- 
come bow-legged  when  allowed  to 
walk  too  early.  Moderate  exercise, 
however,  even  in  infancy,  promotes  the  health  of  the  bones  as 
well  as  of  the  other  tissues.  Hence  a  child  may  be  kept  too 
long  in  its  cradle,  or  wheeled  about  too  much  in  a  carriage, 
when  the  full  use  of  its  limbs  would  furnish  proper  exercise  and 
enable  it  to  walk  earlier. 


FIG.  28.—  External  Ligaments 
of  the  Knee. 


THE    BONES. 


49 


57.  Positions  at  School.  Great  care  must  be  exercised  by  teachers 
that  children  do  not  form  the  habit  of  taking  injurious  positions  at 
school.  The  desks  should  not  be  too  low,  causing  a  forward  stoop  ; 
or  too  high,  throwing  one  shoulder  up  and  giving  a  twist  to  the  spine. 
If  the  seats  are  too  low  there  will  result  an  undue  strain  on  the 
shoulder  and  the  backbone ;  if  too 
high,  the  feet  have  no  proper  support, 
the  thighs  may  be  bent  by  the  weight 
of  the  feet  and  legs,  and  there  is  a 
prolonged  strain  on  the  hips  and 
back.  Curvature  of  the  spine  and 
round  shoulders  often  result  from 
long-continued  positions  at  school  in 
seats  and  at  desks  which  are  not 
adapted  to  the  physical  build  of  the 
occupant. 

A  few  simple  rules  should  guide 
teachers  and  school  officials  in  pro- 
viding proper  furniture  for  pupils. 
Seats  should  be  regulated  according 
to  the  size  and  age  of  the  pupils,  and 
frequent  changes  of  seats  should  be 
made.  At  least  three  sizes  of  desks 
should  be  used  in  every  schoolroom, 
and  more  in  ungraded  schools.  The 
feet  of  each  pupil  should  rest  firmly 
on  the  floor,  and  the  edge  of  the  desk 
should  be  about  one  inch  higher 
than  the  level  of  the  elbows.  A  line 
dropped  from  the  edge  of  the  desk 
should  strike  the  front  edge  of  the 
seat.  Sliding  down  into  the  seat, 
bending  too  much  over  the  desk  while  writing  and  studying,  sitting 
on  one  foot  or  resting  on  the  small  of  the  back,  are  all  ungraceful 
and  unhealthful  positions,  and  are  often  taken  by  pupils  old  enough 
to  know  better.  This  topic  is  well  worth  the  vigilance  of  every 
thoughtful  teacher,  especially  of  one  in  the  lower  grades. 


FIG.  29.  —  Section  of  the  Knee  Joint. 
(Showing  its  internal  structure.) 

A,  tendon  of  the  semi-membranosus 
muscle  cut  across;  B,  F,  tendon  of 
same  muscle;  C,  internal  condyle 
of  femur;  D,  posterior  crucial  liga- 
ment; E,  internal  interarticular 
fibro-cartilage ;  G,  bursa  under  knee- 
cap; H,  ligament  of  knee-cap;  K, 
fatty  mass  under  knee-cap  ;  L,  ante- 
rior crucial  ligament  cut  across  ;  P, 
patella,  or  knee-cap. 


$O  PRACTICAL    PHYSIOLOGY. 

58.  The  Bones  in  After  Life.  Popular  impression  attri- 
butes a  less  share  of  life,  or  a  lower  grade  of  vitality,  to  the 
bones  than  to  any  other  part  of  the  body.  But  really  they 
have  their  own  circulation  and  nutrition,  and  even  nervous 
relations.  Thus,  bones  are  the  seat  of  active  vital  processes, 
not  only  during  childhood,  but  also  in  adult  life,  and  in  fact 
throughout  life,  except  perhaps  in  extreme  old  age.  The  final 
knitting  together  of  the  ends  of  some  of  the  bones  with  their 
shafts  does  not  occur  until  somewhat  late  in  life.  For  example, 
the  upper  end  of  the  tibia  and  its  shaft  do  not  unite  until  the 
twenty-first  year.  The  separate  bones  of  the  sacrum  do  not 
fully  knit  into  one  solid  bone  until  the  twenty-fifth  year. 
Hence,  the  risk  of  subjecting  the  bones  of  young  persons  to 
undue  violence  from  injudicious  physical  exercise  as  in  rowing, 
baseball,  football,  and  bicycle-riding. 

The  bones  during  life  are  constantly  going  through  the 
process  of  absorption  and  reconstruction.  They  are  easily 
modified  in  their  growth.  Thus  the  continued  pressure  of 
some  morbid  deposit,  as  a  tumor  or  cancer,  or  an  enlargement 
of  an  artery,  may  cause  the  absorption  or  distortion  of  bones 
as  readily  as  of  one  of  the  softer  tissues.  The  distortion  re- 
sulting from  tight  lacing  is  a  familiar  illustration  of  the  facility 
with  which  the  bones  may  be  modified  by  prolonged  pressure. 

Some  savage  races,  not  content  with  the  natural  shape  of  the 
head,  take  special  methods  to  mould  it  by  continued  artificial 
pressure,  so  that  it  may  conform  in  its  distortion  to  the  fashion  of 
their  tribe  or  race.  This  custom  is  one  of  the  most  ancient  and 
widespread  with  which  we  are  acquainted.  .In  some  cases  the 
skull  is  flattened,  as  seen  in  certain  Indian  tribes  on  our  Pacific 
coast,  while  with  other  tribes  on  the  same  coast  it  is  compressed 
into  a  sort  of  conical  appearance.  In  such  cases  the  brain  is 
compelled,  of  course,  to  accommodate  itself  to  the  change  in 
the  shape  of  .the  head  ;  and  this  is  done,  it  is  said,  without  any 
serious  result. 


THE    BONES.  51 

59.  Sprains  and  Dislocations.     A   twist   or  strain   of  the 
ligaments  and  soft  parts  about  a>  joint  is  known  as  a  sprain, 
and  may  result  from  a  great  variety  of  accidents.     When  a  per- 
son falls,  the  foot  is  frequently  caught  under  him,  and  the  twist 
comes  upon  the  ligaments  and  tissues  of  the  ankle.     The  liga- 
ments cannot  stretch,  and  so  have  to  endure  the  wrench  upon 
the  joint.      The  result  is  a  sprained  ankle.     Next  to  the  ankle, 
a  sprain  of  the  wrist  is  most  common.     A   person   tries,  by 
throwing  out  his  hand,  to  save  himself  from  a  fall,  and  the 
weight   of   the  body  brings  the  strain  upon  the  firmly  fixed 
wrist.     As  a  result  of  a  sprain,  the  ligaments  may  be  wrenched 
or  torn,  and  even  a  piece  of  an  adjacent  bone  may  be  torn  off; 
the  soft  parts   about  the  injured  joint  are  bruised,  and  the 
neighboring  muscles  put  to  a  severe  stretch.     A  sprain  may  be 
a  slight  affair,  needing  only  a  brief  rest,  or  it  may  be  severe 
and  painful  enough  to  call  for  the  most  skillful  treatment  by  a 
surgeon.     Lack  of  proper  care  in  severe  sprains  often  results 
in  permanent  lameness. 

A  fall  or  a  blow  may  bring  such  a  sudden  wrench  or  twist 
upon  the  ligaments  as  to  force  a  bone  out  of  place.  This 
displacement  is  known  as  a  dislocation.  A  child  may  trip  or 
fall  during  play  and  put  his  elbow  out  of  joint.  A  fall  from 
horseback,  a  carriage,  or  a  bicycle  may  result  in  a  dislocation 
of  the  shoulder  joint.  In  playing  baseball  a  swift  ball  often 
knocks  a  finger  out  of  joint.  A  dislocation  must  be  reduced 
at  once.  Any  delay  or  carelessness  may  make  a  serious  and 
painful  affair  of  it,  as  the  torn  and  bruised  parts  rapidly  swell 
and  become  extremely  sensitive. 

60.  Broken   Bones.     The  bones,    especially   those   of   the 
upper  limbs,  are  often  fractured  or  broken.     The  simple  frac- 
ture is  the  most  common  form,  the  bone  being  broken  in  a 
single  place  with  no  opening  through  the  skin.     When  properly 
adjusted,  the  bone  heals  rapidly.     Sometimes  bones  are  crushed 
into  a  number  of  fragments ;    this   is   a  comminuted  fracture. 


52  PRACTICAL    PHYSIOLOGY. 

When,  besides  the  break,  there  is  an  opening  through  the  soft 
parts  and  surface  of  the  body,  we  have  a  compound  fracture. 
This  is  a  serious  injury,  and  calls  for  the  best  surgical  treat- 
ment. 

A  bone  may  be  bent,  or  only  partly  broken,  or  split.  This  is 
called  "a  green-stick  fracture,"  from  its  resemblance  to  a  half- 
broken  green  stick.  This  fracture  is  more  common  in  the 
bones  of  children. 

Fractures  may  be  caused  by  direct  violence,  as  when  a  bone 
is  broken  at  a  certain  point  by  some  powerful  force,  as  a  blow 
from  a  baseball  bat  or  a  fall  from  a  horse.  Again,  a  bone  may 
be  broken  by  indirect  violence,  as  when  a  person  being  about 
to  fall,  throws  out  his  hand  to  save  himself.  The  force  of  the 
fall  on  the  hand  often  breaks  the  wrist,  by  which  is  meant 
the  fracture  of  the  lower  end  of  the  radius,  often  known  as  the 
"silver-fork  fracture."  This  accident  is  common  in  winter 
from  a  fall  or  slip  on  the  ice. 

Sometimes  bones  are  broken  at  a  distance  from  the  point  of 
injury,  as  in  a  fracture  of  the  ribs  by  violent  compression  of  the 
chest ;  or  fracture  may  occur  from  the  vibration  of  a  blow,  as 
when  a  fall  or  blow  upon  the  top  of  the  head  produces  fracture 
of  the  bones  at  the  base  of  the  brain.1 

61.  Treatment  for  Broken  Bones.  When  a  bone  is  broken 
a  surgeon  is  needed  to  set  it,  that  is,  to  bring  the  broken  parts 
into  their  natural  position,  and  retain  them  by  proper  appliances. 
Nature  throws  out  between  and  around  the  broken  ends  of 
bones  a  supply  of  repair  material  known  as  plastic  lymph, 
which  is  changed  to  fibrous  tissue,  then  to  cartilage,  and  finally 

1  The  mechanism  of  this  remarkable  effect  is  clearly  shown  by  an  experiment 
which  the  late  Dr.  Oliver  Wendell  Holmes  used  to  take  delight  in  performing  in  his 
anatomical  lectures  at  the  Harvard  Medical  College.  He  had  a  strong  iron  bar  made 
into  a  ring  of  some  eight  inches  in  diameter,  with  a  space  left  between  the  ends  just 
large  enough  to  be  filled  by  an  English  walnut.  The  ring  was  then  dropped  to  the 
floor  so  as  to  strike  on  the  convexity  just  opposite  to  the  walnut,  which  invariably 
was  broken  to  pieces. 


THE    BONES.  53 

to  bone.  This  material  serves  as  a  sort  of  cement  to  hold  the 
fractured  parts  together.  The  excess  of  this  at  the  point  of 
union  can  be  felt  under  the  skin  for  some  time  after  the  bone 
is  healed. 

With  old  people  a  broken  bone  is  often  a  serious  matter,  and 
may  cripple  them  for  life  or  prove  fatal.  A  trifling  fall,  for 
instance,  may  cause  a  broken  hip  (popularly  so  called,  though 
really  a  fracture  of  the  neck  of  the  femur),  from  the  shock  of 
which,  and  the  subsequent  pain  and  exhaustion,  an  aged  person 
may  die  in  a  few  weeks.  In  young  people,  however,  the  parts 
of  a  broken  bone  will  knit  together  in  three  or  four  weeks  after 
the  fracture  is  reduced  ;  while  in  adults,  six  or  even  more  may 
be  required  for  firm  union;  After  a  broken  bone  is  strong 
enough  to  be  used,  it  is  fragile  for  some  time  ;  and  great  care 
must  be  taken,  especially  with  children,  that  the  injured  parts 
may  not  be  broken  again  before  perfect  union  takes  place.1 

62.  The  Effect  of  Alcohol  upon  the  Bones.  While  the 
growth  of  the  bones  occurs,  of  course,  mainly  during  the  earlier 
years  of  life,  yet  they  do  not  attain  their  full  maturity  until 
about  the  twenty-fifth  year  ;  and  it  is  stated  that  in  persons 
devoted  to  intellectual  pursuits,  the  skull  grows  even  after  that 
age.  It  is  plainly  necessary  that  during  this  period  of  bone 
growth  the  nutrition  of  the  body  should  be  of  the  best,  that 
the  bones  may  be  built  up  from  pure  blood,  and  supplied  with 
all  the  materials  for  a  large  and  durable  framework.  Else  the 
body  will  be  feeble  and  stunted,  and  so  through  life  fall  short 
of  its  purpose. 

If  this  bony  foundation  be  then  laid  wrong,  the  defect  can 
never  be  remedied.  This  condition  is  seen  in  young  persons 
who  have  been  underfed  and  overworked.  But  the  use  of 
alcoholic  liquors  produces  a  similar  effect,  hindering  bone  cell- 

1  For  the  treatment  of  accidents  and  emergencies  which  may  occur  with  reference 
to  the  bones,  see  Chapter  XIII. 


54  PRACTICAL    PHYSIOLOGY. 

growth  and  preventing  full  development.1  The  appetite  is 
diminished,  nutrition  perverted  and  impaired,  the  stature 
stunted,  and  both  bodily  and  mental  powers  are  enfeebled. 

63.  Effect  of  Tobacco  upon  the  Bones.  Another  narcotic, 
the  destructive  influence  of  which  is  wide  and  serious,  is 
tobacco.  Its  pernicious  influence,  like  that  of  alcohol,  is  pecu- 
liarly hurtful  to  the  young,  as  the  cell  development  during  the 
years  of  growth  is  easily  disturbed  by  noxious  agents.  The 
bone  growth  is  by  cells,  and  a  powerful  narcotic  like  tobacco 
retards  cell-growth,  and  thus  hinders  the  building  up  of  the 
bodily  frame.  The  formation  of  healthy  bone  demands  good, 
nutritious  blood,  but  if  instead  of  this,  the  material  furnished 
for  the  production  of  blood  is  poor  in  quality  or  loaded  with 
poisonous  narcotics,  the  body  thus  defrauded  of  its  proper 
building  material  becomes  undergrown  and  enfeebled. 

Two  unfavorable  facts  accompany  this  serious  drawback  : 
one  is,  that  owing  to  the  insidious  nature  of  the  smoky  poison 2 
(cigarettes  are  its  worst  form) '  the  cause  may  often  be  un- 
suspected, and  so  go  on,  unchecked  ;  and  the  other,  that  the 
progress  of  growth  once  interrupted,  the  gap  can  never  be  fully 
made  up.  Nature  does  her  best  to  repair  damages  and  to 
restore  defects,  but  never  goes  backwards  to  remedy  neglects. 

1  "  Besides  the  danger  connected  with  the  use  of  alcoholic  drinks  which  is  com- 
mon to  them  with  other  narcotic  poisons,  alcohol  retards  the  growth  of  young  cells 
and  prevents  their  proper  development.     Now,  the  bodies  of  all  animals  are  made  up 
largely  of  cells,  .  .  .  and  the  cells  being  the  living  part  of  the  animal,  it  is  especially 
important  that  they  should  not  be  injured  or  badly  nourished  while  they  are  growing. 
So  that  alcohol  in  all  its  forms  is  particularly  injurious  to  young  persons,  as  it 
retards  their  growth,  and  stunts  both  body  and  mind.     This  is  the  theory  of   Dr. 
Lionel  S.  Beale,  a  celebrated  microscopist  and  thinker,  and  is  quite  generally  ac- 
cepted."—DR.  ROGER  S.  TRACY,  of  the  New  York  Board  of  Health. 

2  "  In  its  action  on  the  system  nicotine  is  one  of  the  most  powerful  poisons  known. 
A  drop  of  it  in  a  concentrated  form  was  found  sufficient  to  kill  a  dog,  and  small  birds 
perished  at  the  approach  of  a  tube  containing  it."  —  WOOD'S  Materia  Medica. 

"  Tobacco  appears  to  chiefly  affect  the  heart  and  brain,  and  I  have  therefore 
placed  it  among  cerebral  and  cardiac  poisons."  —  TAYLOR'S  Treatise  on  Poisons. 


THE    BONES.  55 


ADDITIONAL   EXPERIMENTS. 

Experiment  n.  Take  a  portion  of  the  decalcified  bone  obtained  from 
Experiment  4,  and  wash  it  thoroughly  in  water :  in  this  it  is  insoluble. 
Place  it  in  a  solution  of  carbonate  of  soda  and  wash  it  again.  Boil  it  in 
water,  and  from  it  gelatine  will  be  obtained. 

Experiment  12.  Dissolve  in  hydrochloric  acid  a  small  piece  of  the 
powdered  bone-ash  obtained  from  Experiment  3.  Bubbles  of  carbon 
dioxid  are  given  off,  indicating  the  presence  of  a  carbonate.  Dilute  the 
solution ;  add  an  excess  of  ammonia,  and  we  find  a  white  precipitate  of  the 
phosphate  of  lime  and  of  magnesia. 

Experiment  13.  Filter  the  solution  in  the  preceding  experiment,  and  to 
the  filtrate  add  oxalate  of  ammonia.  The  result  is  a  white  precipitate  of 
the  oxalate  of  lime,  showing  there  is  lime  present,  but  not  as  a  phosphate. 

Experiment  14.  To  the  solution  of  mineral  matters  obtained  from 
Experiment  3,  add  acetate  of  soda  until  free  acetic  acid  is  present,  recog- 
nized by  the  smell  (like  dilute  vinegar) ;  then  add  oxalate  of  ammonia. 
The  result  will  be  a  copious  white  precipitate  of  lime  salts. 

Experiment  15.  To  show  how  the  cancellous  structure  of  bone  is  able  to 
support  a  great  deal  of  weight.  Have  the  market-man  saw  out  a  cubic  inch 
from  the  cancellous  tissue  of  a  fresh  beef  bone  and  place  it  on  a  table  with  its 
principal  layers  upright.  Balance  a  heavy  book  upon  it,  and  then  gradually 
place  upon  it  various  articles  and  note  how  many  pounds  it  will  support 
before  giving  way. 

Experiment  16.  Repeat  the  last  experiment,  using  a  cube  of  the  decal- 
cified bone  obtained  from  Experiment  4. 

NOTE.  As  the  succeeding  chapters  are  studied,  additional  experiments  on  bones 
and  their  relation  to  other  parts  of  the  body,  will  readily  suggest  themselves  to  the 
ingenious  instructor  or  the  thoughtful  student.  Such  experiments  may  be  utilized 
for  review  or  other  exercises. 


REVIEW  ANALYSIS:    THE   SKELETON   (206  bones). 


THE    HEAD 
(28  bones). 


I.  CRANIUM 

(8  bones) 


[I. 


FACE         ) 

(14  bones)    ) 


THE   TRUNK 

(54  bones). 


UPPER   LIMBS 

(64  bones). 


LOWER    LIMBS 
(60  bones). 


III.  THE  EAR 

(6  bones) 


I.  SPINAL  COLUMN  |_ 

(26  bones)     j 

II.    THERlBS  ) 
(24  bones)    ( 

III.  STERNUM. 

IV.  Two  HIP  BONES. 
V.  HYOID  BONE. 

I.  UPPER  ARM      .     . 
II.  FOREARM     .     .     . 

III.  HAND 

I.  THIGH     .     .     .     . 
II.  LOWER  LEG      .     . 

III.  FOOT  . 


1  Frontal, 

2  Parietal, 
2  Temporal, 
i  Occipital, 
i  Sphenoid, 

1  Ethmoid. 

2  Superior  Maxillary, 
2  Malar, 

2  Nasal, 

2  Lachrymal  Bones, 

2  Palate  Bones, 

2  Turbinated, 
i  Vomer, 

1  Lower  Maxillary. 

Hammer, 

Anvil, 

Stirrup. 

7  Cervical  Vertebrae, 
12  Dorsal  Vertebrae, 

5  Lumbar  Vertebrae, 

r    Sacrum, 
£t  Coccyx. 

7  True  Ribs, 

3  False  Ribs, 

2  Floating  Ribs. 


Scapula, 
Clavicle, 
Humerus. 

Ulna, 
Radius. 

8  Carpal  Bones, 
5  Metacarpal  Bones. 
14  Phalanges. 

Femur. 

Patella, 

Tibia, 

Fibula. 

7  Tarsal  Bones, 
5  Metatarsal  Bones, 
14  Phalanges. 


CHAPTER   III. 
THE    MUSCLES. 

64.  Motion  in  Animals.     All  motion  of  our  bodies  is  pro- 
duced by  means  of  muscles.     Not  only  the  limbs  are  moved 
by  them,  but  even  the  movements  of  the  stomach  and  of  the 
heart  are  controlled  by  muscles.     Every  part  of  the  body  which 
is  capable  of  motion  has  its  own  special  set  of  muscles. 

Even  when  the  higher  animals  are  at  rest  it  is  possible  to 
observe  some  kind  of  motion  in  them.  Trees  and  stones  never 
move  unless  acted  upon  by  external  force,  while  the  infant  and 
the  tiniest  insect  can  execute  a  great  variety  of  movements. 
Even  in  the  deepest  sleep  the  beating  of  the  heart  and  the 
motion  of  the  chest  never  cease.  In  fact,  the  power  to  execute 
spontaneous  movement  is  the  most  characteristic  property  of 
living  animals. 

65.  Kinds  of  Muscles.    Most  of  the  bodily  movements,  such 
as  affect  the  limbs  and  the  body  as  a  whole,  are  performed  by 
muscles  under  our  control.     These  muscles  make  up  the  red 
flesh  or  lean  parts,  which,   together  with  the  fat,  clothe  the 
bony  framework,  and  give  to  it  general  form  and  proportion. 
We  call  these  muscular  tissues  voluntary  muscles,   because 
they  usually  act  under  the  control  of  the  will. 

The  internal  organs,  as  those  of  digestion,  secretion,  circula- 
tion, and  respiration,  perform  their  functions  by  means  of 
muscular  activity  of  another  kind,  that  is,  by  that  of  muscles 
not  under  our  control.  This  work  goes  on  quite  independently 
of  the  will,  and  during  sleep.  We  call  the  instruments  of  this 
activity  involuntary  muscles.  The  voluntary  muscles,  from 
peculiarities  revealed  by  the  microscope,  are  also  known  as 


PRACTICAL    PHYSIOLOGY. 


striped  or  striated  muscles.  The  involuntary  from  their 
smooth,  regular  appearance  under  the  microscope  are  called 
the  unstriped  or  non-striated  muscles. 

The  two  kinds  of  muscles,  then,  are  the  red,  voluntary, 
striated  muscles,  and  the  smooth,  involuntary,  non-striated 
muscles. 

66.  Structure  of  Voluntary  Muscles.  The  main  substance 
which  clothes  the  bony  framework  of  the  body,  and  which 
forms  about  two-fifths  of  its  weight,  is  the  volun- 
tary muscular  tissue.  These  muscles  do  not 
cover  and  surround  the  bones  in  continuous 
sheets,  but  consist  of  separate  bundles  of  flesh, 
varying  in  size  and  length,  many  of  which  are 
capable  of  independent  movement. 

Each    muscle    has    its    own   set   of   blood- 
vessels,   lymphatics,    and    nerves.      It    is    the 
blood   that   gives  the   red   color  to  the  flesh. 
Blood-vessels  and  nerves  on  their  way  to  other 
parts  of  the  body,  do  not   pass  through  the 
muscles,  but  between  them.     Each  muscle  is 
FIG.  30.  -Striated  enveloped  in  its  own  sheath  of  connective  tis- 
(voiuntary)  Mus-  sue    known  as  the  fascia.      Muscles  are  not 
usually  connected  directly  with  bones,  but  by 


cular  Fibers. 


A,     fiber 

into  disks;  B,  fi- 
brillae  (highly  mag- 
nified); C,  cross 
section  of  a  disk. 


s  means  of  white,  glistening  cords  called  tendons. 


If  a  small  piece  of  muscle  be  examined  under 
a  microscope  it  is  found  to  be  made  up  of  bun- 
dles of  fibers.  Each  fiber  is  enclosed  within  a 
delicate,  transparent  sheath,  known  as  the  sarcolemma.  If 
one  of  these  fibers  be  further  examined  under  a  microscope,  it 
will  be  seen  to  consist  of  a  great  number  of  still  more  minute 
fibers  called  fibrillae.  These  fibers  are  also  seen  marked  cross- 
wise with  dark  stripes,  and  can  be  separated  at  each  stripe  into 
disks.  These  cross  markings  account  for  the  name  striped  or 
striated  muscle. 


THE    MUSCLES. 


59 


The  fibrillae,  then,  are  bound  together  in  a  bundle  to  form  a 
fiber,  which  is  enveloped  in  its  own  sheath,  the  sarcolemma. 
These  fibers,  in  turn,  are  further  bound  together  to  form  larger 
bundles  called  fasciculi,  and  these,  too,  are  enclosed  in  a 
sheath  of  connective  tissue.  The  muscle  itself  is  made  up  of  a 
number  of  these  fasciculi  bound  together 
by  a  denser  layer  of  connective  tissue. 

Experiment  17.  To  show  the  gross  structure  of 
muscle.  Take  a  small  portion  of  a  large  muscle,  as 
a  strip  of  lean  corned  beef.  Have  it  boiled  until 
its  fibers  can  be  easily  separated.  Pick  the  bundles 
and  fasciculi  apart  until  the  fibers  are  so  fine  as  to 
be  almost  invisible  to  the  naked  eye.  Continue  the 
experiment  with  the  help  of  a  hand  magnifying 
glass  or  a  microscope. 

67.   The  Involuntary  Muscles.     These 
muscles   consist    of    ribbon-shaped    bands 
which    surround    hollow    fleshy   tubes    or 
cavities.    We  might  compare  them  to  India  FIG.  31. 
rubber  rings  on  rolls  of  paper.     As  they 
are    never   attached  to  bony  levers,  they      (Highly  magnified.) 
have  no  need  of  tendons. 

The  microscope  shows  these  muscles  to  consist  not  of  fibers, 
but  of  long  spindle-shaped  cells,  united  to  form  sheets  or 
bands.  They  have  no  sarcolemma,  stripes,  or  cross  markings 
like  those  of  the  voluntary  muscles.  Hence  their  name  of  non- 
striated,  or  unstriped,  and  smooth  muscles. 

The  involuntary  muscles  respond  to  irritation  much  less 
rapidly  than  do  the  voluntary.  The  wave  of  contraction  passes 
over  them  more  slowly  and  more  irregularly,  one  part  contracting 
while  another  is  relaxing.  This  may  readily  be  seen  in  the 
muscular  action  of  the  intestines,  called  vermicular  motion.  It 
is  the  irregular  and  excessive  contraction  of  the  muscular 
walls  of  the  bowels  that  produces  the  cramp-like  pains  of  colic. 

The  smooth  muscles  are  found  in  the  tissues  of  the  heart, 


A,  Muscular 


6o 


PRACTICAL    PHYSIOLOGY. 


lungs,  blood-vessels,  stomach,  and  intestines.  In  the  stomach 
their  contraction  produces  the  motion  by  which  the  food  is 
churned  about ;  in  the  arteries  and  veins  they  help  supply  the 
force  by  which  the  blood  is  driven  along,  and  in  the  intestines 
that  by  which  the  partly  digested  food  is  mainly  kept  in  motion. 
Thus  all  the  great  vital  functions  are  carried  on,  regardless 
of  the  will  of  the  individual,  or  of  any  outward  circumstances. 
If  it  required  an  effort  of  the  will  to  control  the  action 
of  the  internal  organs  we  could  not  think  of  anything 
else.  It  would  take  all  our  time  to  attend  to  living. 
Hence  the  care  of  such  delicate  and  important  ma- 
chinery has  wisely  been  put  beyond  our  control. 

Thus,  too,  these  muscles  act  instinctively  without 
training ;  but  the  voluntary  need  long  and  careful 
education.  A  babe  can  use  the  muscles  of  swallow- 
ing on  the  first  day  of  its  life  as  well  as  it  ever  can. 
But  as  it  grows  up,  long  and  patient  education  of  its 
voluntary  muscles  is  needed  to  achieve  walking,  writ- 
ing, use  of  musical  instruments,  and  many  other  acts 
of  daily  life. 


FIG.  32. 

A    Spindle 
Cell  of  In- 
voluntary 
Muscle. 
(Highly 

magnified.) 


Experiment  18.  To  show  the  general  appearance  of  the 
muscles.  Obtain  the  lower  part  of  a  sheep's  or  calf's  leg,  with 
the  most  of  the  lean  meat  and  the  hoof  left  on.  One  or  more 
of  the  muscles  with  their  bundles  of  fibers,  fascia,  and  tendons, 
are  readily  made  out  with  a  little  careful  dissection.  The  dis- 
section should  be  made  a  few  days  before  it  is  wanted  and 
the  parts  allowed  to  harden  somewhat  in  dilute  alcohol. 


68.  Properties  of  Muscular  Tissue.  The  peculiar  property 
of  living  muscular  tissue  is  irritability,  or  the  capacity  of 
responding  to  a  stimulus.  When  a  muscle  is  irritated  it 
responds  by  contracting.  By  this  act  the  muscle  does  not 
diminish  its  bulk  to  any  extent ;  it  simply  changes  its  form. 
The  ends  of  the  muscle  are  drawn  nearer  each  other  and  the 
middle  is  thicker. 


THE    MUSCLES.  6l 

Muscles  do  not  shorten  themselves  all  at  once,  but  the  con- 
traction passes  quickly  over  them  in  the  form  of  a  wave.  They 
are  usually  stimulated  by  nervous  action.  The  delicate  nerve 
fibrils  which  end  in  the  fibers  communicate  with  the  brain,  the 
center  of  the  will  power.  Hence,  when  the  brain  commands,  a 
nervous  impulse,  sent  along  the  nerve  fibers,  becomes  the  excit- 
ing stimulus  which  acts  upon  the  muscles  and  makes  them 
shorter,  harder,  and  more  rigid.1 

Muscles,  however,  will  respond  to  other  than  this  usual 
stimulus.  Thus  an  electrical  current  may  have  a  similar  effect. 
Heat,  also,  may  produce  muscular  contraction.  Mechanical 
means,  such  as  a  sharp  blow  or  pinching,  may  irritate  a  muscle 
and  cause  it  to  contract. 

We  must  remember  that  this  property  of  contraction  is 
inherent  and  belongs  to  the  muscle  itself.  This  power  of  con- 
traction is  often  independent  of  the  brain.  Thus,  on  pricking 
the  heart  of  a  fish  an  hour  after  removal  from  its  body,  obvious 
contraction  will  occur.  In  this  case  it  is  not  the  nerve  force 
from  the  brain  that  supplies  the  energy  for  contraction.  The 
power  of  contraction  is  inherent  in  the  muscle  substance,  and 
the  stimulus  by  irritating  the  nerve  ganglia  of  the  heart  simply 
affords  the  opportunity  for  its  exercise. 

Contraction  is  not,  however,  the  natural  state  of  a  muscle. 
In  time  it  is  tired,  and  begins  to  relax.  Even  the  heart,  the 
hardest-working  muscle,  has  short  periods  of  rest  between 
its  beats.  Muscles  are  highly  elastic  as  well  as  contractile. 
By  this  property  muscle  yields  to  a  stretching  force,  and 
returns  to  its  original  length  if  the  stretching  has  not  been 
excessive. 

1  "  Certain  events  occur  in  the  brain  ;  these  give  rise  to  other  events,  to  changes 
which  travel  along  certain  bundles  of  fibers  called  nerves,  and  so  reach  certain 
muscles.  Arrived  at  the  muscles,  these  changes  in  the  nerves,  which  physiologists 
call  nervous  impulses,  induce  changes  in  the  muscles,  by  virtue  of  which  these  shorten 
contract,  bring  their  ends  together,  and  so,  working  upon  bony  levers,  bend  the  arm 
or  hand,  or  lift  the  weight."  —  PROFESSOR  MICHAEL  FOSTER. 


62 


PRACTICAL    PHYSIOLOGY. 


FIG.  33.  —  Superficial  Muscles  of  the  Body  (Front  View). 


THE    MUSCLES.  63 

69.  The  Object  of  Contraction.  The  object  of  contraction 
is  obvious.  Like  rubber  bands,  if  one  end  of  a  muscle  be 
fixed  and  the  other  attached  to  some  object  which  is  free  to 
move,  the  contraction  of  the  muscle  will  bring  the  movable 
body  nearer  to  the  fixed  point.  A  weight  fastened  to  the  free 
end  of  a  muscle  may  be  lifted  when  the  muscle  contracts. 
Thus  by  their  contraction  muscles  are  able  to  do  their  work. 
They  even  contract  more  vigorously  when  resistance  is  opposed 
to  them  than  when  it  is  not.  With  increased  weight  there  is 
an  increased  amount  of  work  to  be  done.  The  greater  resist- 
ance calls  forth  a  greater  action  of  the  muscle.  This  is  true 
up  to  a  certain  point,  but  when  the  limit  has  been  passed,  the 
muscle  quickly  fails  to  respond. 

Again,  muscles  work  best  with  a  certain  degree  of  rapidity 
provided  the  irritations  do  not  follow  each  other  too  rapidly. 
If,  however,  the  contractions  are  too  rapid,  the  muscles  become 
exhausted  and  fatigue  results.  When  the  feeling  of  fatigue 
passes  away  with  rest,  the  muscle  recovers  its  power.  While 
we  are  resting,  the  blood  is  pouring  in  fresh  supplies  of  building 
material. 


Experiment  19.  To  show  how  muscles  relax  and  contract.  Lay  your 
left  forearm  on  a  table ;  grasp  with  the  right  hand  the  mass  of  flesh  on  the 
front  of  the  upper  arm.  Now  gradually  raise  the  forearm,  keeping  the 
elbow  on  the  table.  Note  that  the  muscle  thickens  as  the  hand  rises. 
This  illustrates  the  contraction  of  the  biceps,  and  is  popularly  called  "  trying 
your  muscle."  Reverse  the  act.  Keep  the  elbow  in  position,  bring  the 
forearm  slowly  to  the  table,  and  the  biceps  appears  to  become  softer  and 
smaller,  —  it  relaxes. 

Experiment  20.  Repeat  the  same  experiment  with  other  muscles.  With 
the  right  hand  grasp  firmly  the  extended  left  forearm.  Extend  and  flex  the 
fingers  vigorously.  Note  the  effect  on  the  muscles  and  tendons  of  the  fore- 
arm. Grasp  with  the  right  hand  the  calf  of  the  extended  right  leg,  and 
vigorously  flex  the  leg,  bringing  it  near  to  the  body.  Note  the  contractions 
and  relaxations  of  the  muscles. 


64  PRACTICAL    PHYSIOLOGY. 

70.  Arrangement  of  Muscles.  Muscles  are  not  connected 
directly  with  bones.  The  mass  of  flesh  tapers  off  towards  the 
ends,  where  the  fibers  pass  into  white,  glistening  cords  known 
as  tendons.  The  place  at  which  a  muscle  is  attached  to  a 
bone,  generally  by  means  of  a  tendon,  is  called  its  origin ;  the 
end  connected  with  the  movable  bone  is  its  insertion. 

There  are  about  400  muscles  in  the  human  body,  all  neces- 
sary for  its  various  movements.  They  vary  greatly  in  shape 
and  size,  according  to  their  position  and  use.  Some  are  from 
one  to  two  feet  long,  others  only  a  fraction  of  an  inch.  Some 
are  long  and  spindle-shaped,  others  thin  and  broad,  while  still 
others  form  rings.  Thus  some  of  the  muscles  of  the  arm  and 
thigh  are  long  and  tapering,  while  the  abdominal  muscles  are 
thin  and  broad  because  they  help  form  walls  for  cavities. 
Again,  the  muscular  fibers  which  surround  and  by  their  con- 
traction close  certain  orifices,  as  those  of  the  eyelids  and  lips, 
often  radiate  like  the  spokes  of  a  wheel. 

Muscles  are  named  according  to  their  shape,  position,  division 
of  origin  or  insertion,  and  their  function.  Thus  we  have  the 
recti  (straight),  and  the  deltoid  (A,  delta),  the  brachial  (arm), 
pectoral  (breast),  and  the  intercostals  (between  the  ribs),  so 
named  from  their  position.  Again,  we  have  the  biceps  (two- 
headed),  triceps  (three-headed),  and  many  others  with  similar 
names,  so  called  from  the  points  of  origin  and  insertion.  We 
find  other  groups  named  after  their  special  use.  The  muscles 
which  bend  the  limbs  are  called  flexors  while  those  which 
straighten  them  are  known  as  extensors. 

After  a  bone  has  been  moved  by  the  contraction  of  a  muscle, 
it  is  brought  back  to  its  position  by  the  contraction  of  another 
muscle  on  the  opposite  side,  the  former  muscle  meanwhile 
being  relaxed.  Muscles  thus  acting  in  opposition  to  each 
other  are  called  antagonistic.  Thus  the  biceps  serves  as  one 
of  the  antagonists  to  the  triceps,  and  the  various  flexors  and 
extensors  of  the  limbs  are  antagonistic  to  one  another. 


THE    MUSCLES. 


71.  The  Tendons.  The  muscles  which  move  the  bones  by 
their  contraction  taper  for  the  most  part,  as  before  mentioned, 
into  tendons.  These  are  commonly  very  strong  cords,  like 
belts  or  straps,  made  up  of  white,  fibrous  tissue. 

Tendons  are  most  numerous  about  the  larger  joints,  where 
they  permit  free  action  and  yet  oc- 
cupy but  little  space.  Large  and 
prominent  muscles  in  these  places 
would  be  clumsy  and  inconvenient. 
If  we  bend  the  arm  or  leg  forcibly, 
and  grasp  the  inside  of  the  elbow 
or  knee  joint,  we  can  feel  the  ten- 
dons beneath  the  skin.  The  numer- 
ous tendons  in  the  palm  or  on  the 
back  of  the  hand  contribute  to  its 
marvelous  dexterity  and  flexibility. 
The  thickest  and  strongest  tendon 
in  the  body  is  the  tendon  of  Achil- 
les, which  connects  the  great  mus- 
cles in  the  calf  of  the  leg  with  the 
heel  bone  (sec.  49). 

When  muscles  contract  forcibly, 
they  pull  upon  the  tendons  which 
transmit  the  movement  to  the  bones 
to  which  they  are  attached.  Ten- 
dons may  be  compared  to  ropes  or 
cords  which,  when  pulled,  are  made 
to  act  upon  distant  objects  to  which 
one  end  is  fastened.  Sometimes  the  tendon  runs  down  the 
middle  of  a  muscle,  and  the  fibers  run  obliquely  into  it,  the 
tendon  resembling  the  quill  in  a  feather.  Again,  tendons  are 
spread  out  in  a  flat  layer  on  the  surface  of  muscles,  in  which 
case  they  are  called  aponeuroses.  Sometimes  a  tendon  is  found 
in  the  middle  of  a  muscle  as  well  as  at  each  end  of  it. 


FIG.  34.— The   Biceps    Muscle 
dissected  to  show  its  Tendons. 


66  PRACTICAL    PHYSIOLOGY. 

72.  SynOvial  Sheaths  and  Sacs.     The  rapid  movement  of 
the  tendons  over  bony  surfaces  and  prominences  would  soon 
produce  an   undue  amount  of  heat  and  friction  unless  some 
means  existed  to  make  the  motion  as  easy  as  possible.     This 
is  supplied  by  sheaths  which  form  a  double  lining  around  the 
tendons.     The  opposed  surfaces  are  lined  with  synovial  mem- 
brane,1 the  secretion  from  which  oils  the  sheaths  in  which  the 
tendons  move. 

Little  closed  sacs,  called  synovial  sacs  or  bursas,  similarly 
lined  and  containing  fluid,  are  also  found  in  special  places  be- 
tween two  surfaces  where  much  motion  is  required.  There 
are  two  of  these  bursae  near  the  patella,  one  superficial,  just 
under  the  skin  ;  the  other  deep  beneath  the  bone  (Fig.  29). 
Without  these,  the  constant  motion  of  the  knee-pan  and  its 
tendons  in  walking  would  produce  undue  friction  and  heat  and 
consequent  inflammation.  Similar,  though  smaller,  sacs  are 
found  over  the  point  of  the  elbow,  over  the  knuckles,  the  ankle 
bones,  and  various  other  prominent  points.  These  sacs  answer 
a  very  important  purpose,  and  are  liable  to  various  forms  of 
inflammation. 

Experiment  21.  Examine  carefully  the  tendons  in  the  parts  dissected  in 
Experiment  18.  Pull  on  the  muscles  and  the  tendons,  and  note  how  they 
act  to  move  the  parts.  This  may  be  also  admirably  shown  on  the  leg  of  a 
fowl  or  turkey  from  a  kitchen  or  obtained  at  the  market. 

Obtain  the  hoof  of  a  calf  or  sheep  with  one  end  of  the  tendon  of  Achilles 
still  attached.  Dissect  it  and  test  its  strength. 

73.  Mechanism  of  Movement.    The  active  agents  of  bodily 
movements,  as  we  have  seen,  are  the  muscles,  which  by  their 
contraction  cause  the  bones  to  move  one  on  the  other.    All  these 
movements,  both  of  motion  and  of  locomotion,  occur  accord- 
ing to  certain  fixed  laws  of  mechanics.     The  bones,  to  which  a 

1  The  synovial  membranes  are  almost  identical  in  structure  with  serous  mem- 
branes (page  176),  but  the  secretion  is  thicker  and  more  like  the  white  of  egg. 


THE    MUSCLES. 


67 


P  W 


great  proportion  of  the  muscles  in  the  body  are  attached,  act 
as  distinct  levers.  The  muscles  supply  the  power  for  moving 
the  bones,  and  the  joints  act  as  fulcrums  or  points  of  support. 
The  weight  of  the  limb,  the  weight  to  be  lifted,  or  the  force  to 
overcome,  is  the  resistance. 

74.  Levers  in  the  Body.  In  mechanics  three  classes  of  levers  are 
described,  according  to  the  relative  position  of  the  power,  the  fulcrum, 
and  the  resistance.  All  the  movements  of  the  bones  can  be  referred 
to  one  or  another  of  these  three  classes. 

Levers  of  the  first  class  are  those  in  which  the  fulcrum  is  between 
the  power  and  the 
weight.  The  crow- 
bar, when  used  to 
lift  a  weight  at  one 
end  by  the  applica- 
tion of  power  at  the 
other,  with  a  block 
as  a  fulcrum,  is  a 
familiar  example  of 
this  class.  There 
are  several  exam- 
ples of  this  in  the 
human  body.  The 
head  supported  on  the  atlas  is  one.  The  joint  between  the  atlas  and 
the  skull  is  the  fulcrum,  the  weight  of  the  head  is  the  resistance. 
The  power  is  behind,  where  the  muscles  from  the  neck  are  attached 
to  the  back  of  the  skull.  The  object  of  this  arrangement  is  to  keep 
the  head  steady  and  balanced  on  the  spinal  column,  and  to  move  it 
backward  and  forward. 

Levers  of  the  second  class  are  those  in  which  the  weight  is  between 
the  fulcrum  and  the  power.  A  familiar  example  is  the  crowbar  when 
used  for  lifting  a  weight  while  one  end  rests  on  the  ground.  This  class 
of  levers  is  not  common  in  the  body.  Standing  on  tiptoe  is,  however, 
an  example.  Here  the  toes  in  contact  with  the  ground  are  the  fulcrum, 
the  power  is  the  action  of  the  muscles  of  the  calf,  and  between  these  is 
the  weight  of  the  body  transmitted  down  the  bones  of  the  leg  to  the  foot. 


FIG.  35.  —  Showing  how  the  Bones  of  the  Arm  serve  as 
Levers.     P,  power;  W,  weight;  F,  fulcrum. 


68  PRACTICAL    PHYSIOLOGY. 

Levers  of  the  third  class  are  those  in  which  the  power  is  applied 
at  a  point  between  the  fulcrum  and  weight.  A  familiar  example  is 
where  a  workman  raises  a  ladder  against  a  wall.  This  class  of  levers 
is  common  in  the  body.  In  bending  the  forearm  on  the  arm,  familiarly 
known  as  "  trying  your  muscle,"  the  power  is  supplied  by  the  biceps 
muscle  attached  to  the  radius,  the  fulcrum  is  the  elbow  joint  at  one 
end  of  the  lever,  and  the  resistance  is  the  weight  of  the  forearm  at 
the  other  end. 

Experiment  22.  To  illustrate  how  the  muscles  use  the  bones  as  levers.  First, 
practice  with  a  ruler,  blackboard  pointer,  or  any  other  convenient  object, 
illustrating  the  different  kinds  of  levers  until  the  principles  are  familiar. 
Next,  illustrate  these  principles  on  the  person,  by  making  use  of  convenient 
muscles.  Thus,  lift  a  book  on  the  toes,  by  the  fingers,  on  the  back  of  the 
hand,  by  the  mouth,  and  in  other  ways. 

These  experiments,  showing  how  the  bones  serve  as  levers,  may  be 
multiplied  and  varied  as  circumstances  may  require. 

75.  The  Erect  Position.  The  erect  position  is  peculiar  to 
man.  No  other  animal  naturally  assumes  it  or  is  able  to  keep 
it  long.  It  is  the  result  of  a  somewhat  complex  arrangement 
of  muscles  which  balance  each  other,  some  pulling  backwards 
and  some  forwards.  Although  the  whole  skeleton  is  formed 
with  reference  to  the  erect  position,  yet  this  attitude  is  slowly 
learned  in  infancy. 

In  the  erect  position  the  center  of  gravity  lies  in  the  joint 
between  the  sacrum  and  the  last  lumbar  vertebra.  A  line 
dropped  from  this  point  would  fall  between  the  feet,  just  in 
front  of  the  ankle  joints.  We  rarely  stand  with  the  feet  close 
together,  because  that  basis  of  support  is  too  small  for  a  firm 
position.  Hence,  in  all  efforts  requiring  vigorous  muscular 
movements  the  feet  are  kept  more  or  less  apart  to  enlarge  the 
basis  of  support. 

Now,  on  account  of  the  large  number  and  flexibility  of  the 
joints,  the  body  could  not  be  kept  in  an  upright  position  with- 
out the  cooperation  of  certain  groups  of  muscles.  The  mus- 
cles of  the  calf  of  the  leg,  acting  on  the  thigh  bone,  above  the 


THE    MUSCLES. 


69 


knee,  keep  the  body  from  falling 
forward,  while  another  set  in  front 
of  the  thigh  helps  hold  the  leg 
straight.  These  thigh  muscles 
also  tend  to  pull  the  trunk  for- 
ward, but  in  turn  are  balanced  by 
the  powerful  muscles  of  the  lower 
back,  which  help  keep  the  body 
straight  and  braced. 

The  head  is  kept  balanced  on 
the  neck  partly  by  the  central 
position  of  the  joint  between  the 
atlas  and  axis,  and  partly  by 
means  of  strong  muscles.  Thus, 
the  combined  action  of  these  and 
other  muscles  serves  to  balance 
the  body  and  keep  it  erect.  A 
blow  on  the  head,  or  a  sudden 
shock  to  the  nervous  system, 
causes  the  body  to  fall  in  a  heap, 
because  the  brain  has  for  the  time 
lost  its  power  over  the  muscles, 
and  they  cease  to  contract. 

76.   Important  Muscles. 

There  are  scores  of  tiny  muscles 
about  the  head,  face,  and  eyes, 
which,  by  their  alternate  contrac- 
tions and  relaxations,  impart  to 
the  countenance  those  expres- 
sions which  reflect  the  feelings 
and  passions  of  the  individual. 
Two  important  muscles,  the  tem- 
poral, near  the  temples,  and  the 
masseter,  or  chewing  muscle,  are 


B — I 


FIG.  36. — Diagram  showing  the  Action 
of  the  Chief  Muscles  which  keep  the 
Body  Erect.  (The  arrows  indicate 
the  direction  in  which  these  muscles 
act,  the  feet  serving  as  a  fixed  basis.) 
[After  Huxley.] 

Muscles  -which  tend  to  keep  the  body 

from  falling  forward. 
A,  muscles  of  the  calf;   B,  of  the  back  of 
the  thigh;  C,  of  the  spinal  column. 

Muscles  which  tend  to  keep  the  body 

from  falling  backward. 
D,  muscles  of  the  front  of  the  leg;  E,  of 
the  front  of  the  thigh  ;  F,  of  the  front  of 
the  abdomen  ;  G ,  of  the  front  of  the  neck 


7O  PRACTICAL    PHYSIOLOGY. 

the  chief  agents  in  moving  the  lower  jaw.  They  are  very  large 
in  the  lion,  tiger,  and  other  flesh-eating  animals.  On  the  inner 
side  of  each  cheek  is  the  buccinator,  or  trumpeter's  muscle, 
which  is  largely  developed  in  those  who  play  on  wind  instru- 
ments. Easily  seen  and  felt  under  the  skin  in  thin  persons, 
on  turning  the  head  to  one  side,  is  the  sterno-cleido-mastoid 
muscle,  which  passes  obliquely  down  on  each  side  of  the 
neck  to  the  collar  bone  —  prominent  in  sculpture  and 
painting. 

The  chest  is  supplied  with  numerous  muscles  which  move 
the  ribs  up  and  down  in  the  act  of  breathing.  A  great,  fan- 
shaped  muscle,  called  the  pectoralis  major,  lies  on  the  chest. 
It  extends  from  the  chest  to  the  arm  and  helps  draw  the  arm 
inward  and  forward.  The  arm  is  raised  from  the  side  by  a 
large  triangular  muscle  on  the  shoulder,  the  deltoid,  so  called 
from  its  resemblance  to  the  Greek  letter  delta,  A.  The  biceps, 
or  two-headed  muscle,  forms  a  large  part  of  the  fleshy  mass  in 
front  of  the  arm.  Its  use  is  to  bend  the  forearm  on  the  arm, 
an  act  familiarly  known  as  "  trying  your  muscle."  Its  direct 
antagonist  is  the  three-headed  muscle  called  the  triceps.  It 
forms  the  fleshy  mass  on  the  back  of  the  arm,  its  use  being 
to  draw  the  flexed  forearm  into  a  right  line. 

On  the  back  and  outside  of  the  forearm  are  the  extensors, 
which  straighten  the  wrist,  the  hand,  and  the  fingers.  On  the 
front  and  inside  of  the  forearm  are  the  flexors,  which  bend  the 
hand,  the  wrist,  and  the  fingers.  If  these  muscles  are  worked 
vigorously,  their  tendons  can  be  readily  seen  and  felt  under 
the  skin.  At  the  back  of  the  shoulder  a  large,  spread-out 
muscle  passes  upward  from  the  back  to  the  humerus.  From 
its  wide  expanse  on  the  back  it  is  known  as  the  latissimus 
dor  si  (broadest  of  the  back).  When  in  action  it  draws  the 
arm  downward  and  backward,  or,  if  one  hangs  by  the  hands,  it 
helps  to  raise  the  body.  It  is  familiarly  known  as  the  "  climb- 
ing muscle." 


THE    MUSCLES. 


Passing  to  the  lower  extremity,  the  thigh  muscles  are  the 
largest  and  the  most  powerful  in  the  body.     In  front  a  great, 


FIG.  37.  —  A  Few  of  the  Important  Muscles  of  the  Back. 

four-headed  muscle,  quadriceps  extensor,  unites  into  a  single 
tendon  in  which  the  knee-cap  is  set,  and  serves  to  straighten 


/2  PRACTICAL    PHYSIOLOGY. 

the  knee,  or  when  rising  from  a  sitting  posture  helps  elevate 
the  body.  On  the  back  of  the  thigh  are  several  large  muscles 
which  bend  the  knee,  and  whose  tendons,  known  as  the  "  ham- 
strings," are  readily  felt  just  behind  the  knee.  On  the  back 
of  the  leg  the  most  important  muscles,  forming  what  is  known 
as  the  calf,  are  the  gastrocnemius  and  the  soleus.  The  first 
forms  the  largest  part  of  the  calf.  The  soleus,  so  named  from 
resembling  a  sole-fish,  is  a  muscle  of  broad,  flattened  shape, 
lying  beneath  the  gastrocnemius.  The  tendons  of  these  two 
muscles  unite  to  form  the  tendon  of  Achilles,  as  that  hero  is 
said  to  have  been  invulnerable  except  at  this  point.  The 
muscles  of  the  calf  have  great  power,  and  are  constantly  called 
into  use  in  walking,  cycling,  dancing,  and  leaping. 

77.  The  Effect  of  Alcoholic  Drinks  upon  the  Muscles. 
It  is  found  that  a  man  can  do  more  work  without  alcohol 
than  with  it.  After  taking  it  there  may  be  a  momentary 
increase  of  activity,  but  this  lasts  only  ten  or  fifteen  minutes 
at  the  most.  It  is  followed  by  a  rapid  reduction  of  power  that 
more  than  outweighs  the  momentary  gain,  while  the  quality 
of  the  work  is  decidedly  impaired  from  the  time  the  alcohol 
is  taken. 

Even  in  the  case  of  hard  work  that  must  be  speedily  done, 
alcohol  does  not  help,  but  hinders  its  execution.  The  tired 
man  who  does  not  understand  the  effects  of  alcohol  often 
supposes  that  it  increases  his  strength,  when  in  fact  it  only 
deadens  his  sense  of  fatigue  by  paralyzing  his  nerves.  When 
put  to  the  test  he  is  surprised  at  his  self-deception. 

Full  intoxication  produces,  by  its  peculiar  depression  of  the 
brain  and  nervous  system,  an  artificial  and  temporary  paralysis 
of  the  muscles,  as  is  obvious  in  the  pitifully  helpless  condition 
of  a  man  fully  intoxicated.  But  even  partial  approach  to  in- 
toxication involves  its  proportionate  impairment  of  nervous 
integrity,  and  therefore  just  so  much  diminution  of  muscular 


THE    MUSCLES.  73 

force.  All  athletes  recognize  this  fact,  as  while  training  for  a 
contest,  rigid  abstinence  is  the  rule,  both  from  liquors  and 
tobacco.  This  muscular  weakness  is  shown  also  in  the  un- 
steady hand,  the  trembling  limbs  of  the  inebriate,  his  thick 
speech,  wandering  eye,  and  lolling  head. 

78.  Destructive  Effect  of  Alcoholic  Liquors  upon  Mus- 
cular Tissue.  Alcoholic  liquors  retard  the  natural  chemical 
changes  so  essential  to  good  health,  by  which  is  meant  the 
oxidation  of  the  nutritious  elements  of  food.  Careful  demon- 
stration has  proved  also  that  the  amount  of  carbon  dioxid 
escaping  from  the  lungs  of  intoxicated  persons  is  from  thirty 
to  fifty  per  cent  less  than  normal.  This  shut-in  carbon  stifles 
the  nervous  energy,  and  cuts  off  the  power  that  controls  mus- 
cular force.  This  lost  force  is  in  close  ratio  to  the  retained 
carbon  :  so  much  perverted  chemical  change,  so  much  loss  of 
muscular  power.  Not  only  the  strength  but  the  fine  delicacy 
of  muscular  action  is  lost,  the  power  of  nice  control  of  the 
hand  and  fingers,  as  in  neat  penmanship,  or  the  use  of  musical 
instruments. 

To  this  perverted  chemical  action  is  also  due  the  fatty 
degeneration  so  common  in  inebriates,  affecting  the  muscles, 
the  heart,  and  the  liver.  These  organs  are  encroached  upon 
by  globules  of  fat  (a  hydrocarbon),  which,  while  very  good  in 

NOTE.  It  was  proposed  during  the  Civil  War  to  give  each  soldier  in  a  certain 
army  one  gill  of  whiskey  a  day,  because  of  great  hardship  and  exposure.  The  emi- 
nent surgeon,  Dr.  Frank  H.  Hamilton  of  New  York,  thus  expressed  his  views  of 
the  question  :  "  It  is  earnestly  desired  that  no  such  experiment  will  ever  be  repeated 
in  the  armies  of  the  United  States.  In  our  own  mind,  the  conviction  is  established, 
by  the  experience  and  observation  of  a  life,  that  the  regular  routine  employment  of 
alcoholic  stimulants  by  man  in  health  is  never,  under  any  circumstances,  useful.  We 
make  no  exceptions  in  favor  of  cold  or  heat  or  rain." 

"  It  seems  to  me  to  follow  from  these  Arctic  experiences  that  the  regular  use  of 
spirits,  even  in  moderation,  under  conditions  of  great  physical  hardship,  continued 
and  exhausting  labor,  or  exposure  to  severe  cold  cannot  be  too  strongly  deprecated." 
—  A.  W.  GREELY,  retired  Brigadier-General,  U.  S.  A.,  and  formerly  leader  of  the 
Greely  Expedition. 


74 


PRACTICAL    PHYSIOLOGY. 


their  proper  place  and  quantity,  become  a  source  of  disorder 
and  even  of  death  when  they  abnormally  invade  vital  structures. 
Other  poisons,  as  phosphorus,  produce  this  fatty  decay  more 
rapidly;  but  alcohol  causes  it  in  a  much  more  general  way. 


FIG.  38.  —  Principal  Muscles  on  the  Left  Side  ot  Neck. 

A,  buccinator;  B,  masseter;  C,  depressor  anguli  oris;  D,  anterior  portion  of  the 
digastric;  E,  mylo-hyoid;  F,  tendon  of  the  digastric;  G,  sterno-hyoid ;  H,  sterno- 
thyroid;  K,  omo-hyoid ;  L,  sternal  origin  of  sterno-cleido-mastoid  muscle;  M, 
superior  fibers  of  deltoid;  N,  posterior  scalenus;  O,  clavicular  origin  of  sterno- 
cleido-mastoid;  P,  sterno-cleido-mastoid;  R,  trapezius;  S,  anterior  constrictor; 
T,  splenius  capitis;  V,  stylo-hyoid ;  W,  posterior  portion  of  the  digastric;  X,  fasci- 
culi of  ear  muscles  ;  Z,  occipital. 

This  is  proved  by  the  microscope,  which  plainly  shows  the 
condition  mentioned,  and  the  difference  between  the  healthy 
tissues  and  those  thus  diseased. 


THE    MUSCLES.  75 

79.  Effect  of  Tobacco  on  the  Muscles.  That  other  promi- 
nent narcotic,  tobacco,  impairs  the  energy  of  the  muscles 
somewhat  as  alcohol  does,  by  its  paralyzing  effect  upon  the 
nervous  system.  As  all  muscular  action  depends  on  the 
integrity  of  the  nervous  system,  whatever  lays  its  deadening 
hand  upon  that,  saps  the  vigor  and  growth  of  the  entire  frame, 
dwarfs  the  body,  and  retards  mental  development.  This 
applies  especially  to  the  young,  in  the  growing  age  between 
twelve  or  fourteen  and  twenty,  the  very  time  when  the  healthy 
body  is  being  well  knit  and  compacted. 

Hence  many  public  schools,  as  well  as  our  national  naval 
and  military  academies,  rigidly  prohibit  the  use  of  tobacco  by 
their  pupils.  So  also  young  men  in  athletic  training  are  strictly 
forbidden  to  use  it.1  This  loss  of  muscular  vigor  is  shown  by 
the  unsteady  condition  of  the  muscles,  the  trembling  hand,  and 
the  inability  to  do  with  precision  and  accuracy  any  fine  work, 
as  in  drawing  or  nice  penmanship. 

ADDITIONAL   EXPERIMENTS. 

Experiment  23.  To  examine  the  minute  structure  of  voluntary  muscular 
fiber.  Tease,  with  two  needles  set  in  small  handles,  a  bit  of  raw,  lean  meat, 
on  a  slip  of  glass,  in  a  little  water.  Continue  until  the  pieces  are  almost 
invisible  to  the  naked  eye. 

Experiment  24.  Place  a  clean,  dry  cover-glass  of  about  the  width  of  the 
slip,  over  the  water  containing  the  torn  fragments.  Absorb  the  excess  of 
moisture  at  the  edge  of  the  cover,  by  pressing  a  bit  of  blotting-paper  against 
it  for  a  moment.  Place  it  on  the  stage  of  a  microscope  and  examine  with 
highest  obtainable  power,  by  light  reflected  upward  from  the  mirror  beneath 
the  stage.  Note  the  apparent  size  of  the  finest  fibers  ;  the  striation  of  the 
fibers,  or  their  markings,  consisting  of  alternate  dim  and  bright  cross  bands. 
Note  the  arrangement  of  the  fibers  in  bundles,  each  thread  running  parallel 
with  its  neighbor. 

1  "  Smoking  among  students  or  men  training  for  contests  is  a  mistake.  It  not  only 
affects  the  wind,  but  relaxes  the  nerves  in  a  way  to  make  them  less  vigorous  for  the 
coming  contest.  It  shows  its  results  at  once,  and  when  the  athlete  is  trying  to  do  his 
best  to  win  he  will  do  well  to  avoid  it."  JOSEPH  HAMBLEN  SEARS,  Harvard  Coach, 
and  Ex-Captain  of  the  Harvard  Football  Team,  Article  in  In  Sickness  and  in  Health. 


76  PRACTICAL    PHYSIOLOGY. 

experiment  25.  To  examine  the  minute  structure  of  invohintary  mus- 
cular fiber,  a  tendon,  or  a  ligament.  Obtain  a  very  small  portion  of  the 
muscular  coat  of  a  cow's  or  a  pig's  stomach.  Put  it  to  soak  in  a  solution  of 
one  dram  of  bichromate  of  potash  in  a  pint  of  water.  Take  out  a  morsel 
on  the  slip  of  glass,  and  tease  as  directed  for  the  voluntary  muscle.  Exam- 
ine with  a  high  power  of  the  microscope  and  note  :  (i)  the  isolated  cells, 
long  and  spindle-shaped,  that  they  are  much  flattened;  (2)  the  arrangement 
of  the  cells,  or  fibers,  in  sheets,  or  layers,  from  the  torn  ends  of  which  they 
project  like  palisades. 

Experiment  26.  Tease  out  a  small  portion  of  the  tendon  or  ligament  in 
water,  and  examine  with  a  glass  of  high  power.  Note  the  large  fibers  in  the 
ligament,  which  branch  and  interlace. 

Experiment  27.  With  the  head  slightly  bent  forwards,  grasp  between 
the  fingers  of  the  right  hand  the  edge  of  the  left  sterno-cleido-mastoid,  just 
above  the  collar  bone.  Raise  the  head  and  turn  it  from  left  to  right,  and 
the  action  of  this  important  muscle  is  readily  seen  and  felt.  In  some  per- 
sons it  stands  out  in  bold  relief. 

Experiment  28.  The  tendons  which  bound  the  space  (popliteal)  behind 
the  knee  can  be  distinctly  felt  when  the  muscles  which  bend  the  knee  are  in 
action.  On  the  outer  side  note  the  tendons  of  the  biceps  of  the  leg,  running 
down  to  the  head  of  the  fibula.  On  the  inside  we  feel  three  tendons  of 
important  muscles  on  the  back  of  the  thigh  which  flex  the  leg  upon  the 
thigh. 

Experiment  29.  To  sho%v  the  ligamentous  action  of  the  muscles.  Standing 
with  the  back  fixed  against  a  wall  to  steady  the  pelvis,  the  knee  can  be 
flexed  so  as  to  almost  touch  the  abdomen.  Take  the  same  position  and 
keep  the  knee  rigid.  .When  the  heel  has  been  but  slightly  raised  a  sharp 
pain  in  the  back  of  the  thigh  follows  any  effort  to  carry  it  higher.  Flexion 
of  the  leg  to  a  right  angle,  increases  the  distance  from  the  lines  of  insertion 
on  the  pelvic  bones  to  the  tuberosities  of  the  tibia  by  two  or  three  inches  — 
an  amount  of  stretching  these  muscle  cannot  undergo.  Hence  the  knee 
must  be  flexed  in  flexion  of  the  hip. 

Experiment  30.  A  similar  experiment  may  be  tried  at  the  wrist.  Flex 
the  wrist  with  the  fingers  extended,  and  again  with  the  fingers  in  the  fist. 
The  first  movement  can  be  carried  to  90°,  the  second  only  to  30°,  or  in 
some  persons  up  to  60°.  Making  a  fist  had  already  stretched  the  extensor 
muscles  of  the  arm,  and  they  can  be  stretched  but  little  farther.  Hence, 
needless  pain  will  be  avoided  by  working  a  stiff  wrist  with  the  parts  loose, 
or  the  fingers  extended,  and  not  with  a  clenched  fist. 


REVIEW   ANALYSIS:    IMPORTANT   MUSCLES. 


LOCATION. 


HEAD 

AND 

NECK. 


TRUNK. 


UPPER 
LIMBS. 


LOWER 
LIMBS. 


NAME. 

Occipito-frontalis   .     . 

Orbicularis  palpebrarum 
Levator  palpebrarum . 
Temporal      .... 
Masseter . 


Sterno-cleido  -mastoid 

Platysma  myoides  . 

Pectoralis  major    .  . 

Pectoralis  minor     .  . 

Latissimus  dorsi    .  . 

Serratus  magnus  .  . 

Trapezius     .     .     .  . 

Rhomboideus     .     .  . 

Intercostals  .     .     .  . 

External  oblique    .  . 

Internal  oblique      .  . 

Rectus  abdominis  . 


Deltoid     .... 

Biceps  .... 
Triceps  .... 
Brachialis  anticus 
Supinator  longus  . 
Flexor  carpi  radialis 
Flexor  carpi  ulnaris 

Gluteus  maximus . 
Adductors  of  thigh 
Sartorius  .  .  . 
Rectus  femoris  .  . 
Vastus  externus  . 
Vastus  internus  . 
Biceps  femoris  .  . 

Gracilis    . 


Tibialis  anticus 
Peroneus  longus 
Gastrocnemius  . 
Soleus 


CHIEF  FUNCTION. 

moves  scalp  and  raises  eye- 
brow. 

shuts  the  eyes, 
opens  the  eyes. 

raise  the  lower  jaw. 

j   depresses  head  upon  neck  and 
I       neck  upon  chest, 
depresses  lower  jaw  and  lower 
lip. 

j  draws  arm  across  front  of 
(  chest. 

depresses  point  of  shoulder. 

draws  arm  downwards  and 
backwards. 

assists  in  raising  ribs, 
backward  movements  of  head 

and  shoulder, 
raise  and  depress  the  ribs, 
various  forward  movements 

of  trunk, 
compresses  abdominal  viscera 

and  acts  upon  pelvis. 

carries  arm  outwards  and  up- 
wards. 

flexes  elbow  and  raises  arm. 
extends  the  forearm, 
flexor  of  elbow, 
flexes  the  forearm. 

flexors  of  wrist. 


adducts  the  thigh. 

draw  the  leg  inwards. 

crosses  the  legs. 

flexes  the  thigh. 

extensor  of  leg. 

extensor  of  leg  upon  thigh. 

flexes  leg  upon  thigh. 

flexes    the   leg   and   adducts 

thigh. 

draws  up  inner  border  of  foot, 
raises  outer  edge  of  foot, 
keep  the  body  erect,  and  aid 

in  walking  and  running. 


CHAPTER    IV. 
PHYSICAL   EXERCISE. 

80.  Importance  of  Bodily  Exercise.  Nothing  is  so  essen- 
tial to  success  in  life  as  sound  physical  health.  It  enables 
us  to  work  with  energy  and  comfort,  and  better  to  endure 
unusual  physical  and  mental  strains.  While  others  suffer  the 
penalties  of  feebleness,  a  lower  standard  of  functional  activi- 
ties, and  premature  decay,  the  fortunate  possessor  of  a  sound 
mind  in  a  sound  body  is  better  prepared,  with  proper  applica- 
tion, to  endure  the  hardships  and  win  the  triumphs  of  life.1 

This  element  of  physical  capacity  is  as  necessary  to  a  useful 
and  energetic  life,  as  are  mental  endowment  and  intellectual 
acquirement.  Instinct  impels  us  to  seek  health  and  pleasure 
in  muscular  exercise.  A  healthy  and  vigorous  child  is  never 
still  except  during  sleep.  The  restless  limbs  and  muscles  of 
school  children  pent  up  for  several  hours,  feel  the  need  of 
movement,  as  a  hungry  man  craves  food.  This  natural  desire 
for  exercise,  although  too  often  overlooked,  is  really  one  of  the 
necessities  of  life.  One  must  be  in  ill  health  or  of  an  imper- 
fect nature,  when  he  ceases  to  feel  this  impulse.  Indeed, 
motion  within  proper  bounds  is  essential  to  the  full  develop- 
ment and  perfect  maintenance  of  the  bodily  health.  Unlike 

1  "  There  is  no  profession,  there  is  no  calling  or  occupation  in  which  men  can  be 
engaged,  there  is  no  position  in  life,  no  state  in  which  a  man  can  be  placed,  in 
which  a  fairly  developed  frame  will  not  be  valuable  to  him  ;  there  are  many  of  these, 
even  the  most  purely  and  highly  intellectual,  in  which  it  is  essential  to  success — 
essential  simply  as  a  means,  material,  but  none  the  less  imperative,  to  enable  the 
mind  to  do  its  work.  Year  by  year,  almost  day  by  day,  we  see  men  (and  women), 
falter  and  fail  in  the  midst  of  their  labors ;  .  .  .  and  all  for  want  of  a  little  bodily 
stamina  —  a  little  bodily  power  and  bodily  capacity  for  the  endurance  of  fatigue,  or 
protracted  unrest,  or  anxiety,  or  grief."  —  MACLAREN'S  Physical  Education. 


PHYSICAL    EXERCISE.  79 

other  machines,  the  human  body  becomes  within  reasonable 
limits,  stronger  and  more  capable  the  more  it  is  used. 

As  our  tenure  of  life  at  best  is  short,  it  is  our  duty  to 
strive  to  live  as  free  as  possible  from  bodily  ills.  It  is,  there- 
fore, of  paramount  importance  to  rightly  exercise  every  part 
of  the  body,  and  this  without  undue  effort  or  injurious  strain. 

Strictly  speaking,  physical  exercise  refers  to  the  functional 
activity  of  each  and  every  tissue,  and  properly  includes  the 
regulation  of  the  functions  and  movements  of  the  entire  body. 
The  word  exercise,  however,  is  used  usually  in  a  narrower  sense 
as  applied  to  those  movements  that  are  effected  by  the  contrac- 
tion of  the  voluntary  muscles. 

Brief  reference  will  be  made  in  this  chapter  only  to  such 
natural  and  systematic  physical  training  as  should  enter  into  the 
life  of  every  healthy  person. 

81.  Muscular  Activity.  The  body,  as  we  have  learned, 
is  built  up  of  certain  elementary  tissues  which  are  combined 
to  make  bones,  muscles,  nerves,  and  other  structures.  The 
tissues,  in  turn,  are  made  up  of  countless  minute  cells,  each 
of  which  has  its  birth,  lives  its  brief  moment  to  do  its  work  in 
the  animal  economy,  is  separated  from  the  tissue  of  which  it 
was  a  part,  and  is  in  due  time  eliminated  by  the  organs  of  ex- 
cretion, —  the  lungs,  the  skin,  or  the  kidneys.  Thus  there  is 
a  continuous  process  of  growth,  of  decay,  and  removal,  among 
the  individual  cells  of  each  tissue. 

NOTE.  The  Incessant  Changes  in  Muscular  Tissue.  "  In  every  tiny  block 
of  muscle  there  is  a  part  which  is  really  alive,  there  are  parts  which  are  becoming  alive, 
there  are  parts  which  have  been  alive,  and  are  now  dying  or  dead ;  there  is  an 
upward  rush  from  the  lifeless  to  the  living,  a  downward  rush  from  the  living  to  the 
dead.  This  is  always  going  on,  whether  the  muscle  be  quiet  and  at  rest,  or  whether 
it  be  active  and  moving, —  some  of  the  capital  of  living  material  is  being  spent,  changed 
into  dead  waste ;  some  of  the  new  food  is  always  being  raised  into  living  capital. 
But  when  the  muscle  is  called  upon  to  do  work,  when  it  is  put  into  movement,  the 
expenditure  is  quickened,  there  is  a  run  upon  the  living  capital,  the  greater,  the  more 
urgent  the  call  for  action." —  PROFESSOR  MICHAEL  FOSTER. 


8o 


PRACTICAL    PHYSIOLOGY. 


These  ceaseless  processes  are  greatly  modified  by  the  activity 
of  the  bodily  functions.  Every  movement  of  a  muscle,  for 
instance,  involves  change  in  its  component  cells.  And  since 
the  loss  of  every  atom  of  the  body  is  in  direct  relation  to  its 
activity,  a  second  process  is  necessary  to  repair  this  constant 

waste;  else  the  body  would 
rapidly  diminish  in  size 
and  strength,  and  life  itself 
would  soon  end.  This 
process  of  repair  is  accom- 
plished, as  we  shall  learn 
in  Chapters  VI.  and  VII. , 
by  the  organs  of  nutrition, 
which  convert  the  food 
into  blood. 

82.  Effect  of  Exercise 
upon  the  Muscles.  Sys- 
tematic exercise  influences 
the  growth  and  structure 
of  the  muscles  of  the  body 
in  a  manner  somewhat  re- 
markable. Muscular  exercise  makes  muscular  tissue ;  from 
the  lack  of  it,  muscles  become  soft  and  wasted.  Muscles 
properly  exercised  not  only  increase  in  size,  both  as  a  whole 
and  in  their  individual  structure,  but  afe  better  enabled  to  get 
rid  of  material  which  tends  to  hamper  their  movements. 
Thus  muscular  exercise  helps  to  remove  any  needless  ac- 
cumulation of  fat,  as  well  as  useless  waste  matters,  which  may 
exist  in  the  tissues.  As  fat  forms  no  permanent  structural  part 
of  the  organism,  its  removal  is,  within  limits,  effected  with  no 
inconvenience. 

Muscular  strength  provides  the  joints  with  more  powerful 
ligaments  and  better  developed  bony  parts.  After  long  con- 


FIG.  39.  —  Showing  how  the  Muscles  of  the 
Back  may  be  developed  by  a  Moderate 
Amount  of  Dumb-Bell  Exercise  at  Home. 
(From  a  photograph.) 


PHYSICAL    EXERCISE. 


8l 


finement  to  the  bed  from  disease,  the  joints  have  wasted  liga- 
ments, thin  cartilages,  and  the  bones  are  of  smaller  proportions. 
Duly  exercised  muscles  influence  the  size  of  the  bones  upon 
which  they  act.  Thus  the  bones  of  a  well-developed  man  are 
stronger,  firmer,  and  larger  than  those  of  a  feeble  person. 

He  who  has  been  physically  well  trained,  has  both  a  more 
complete  and  a  more  intelligent  use  of  his  muscles.  He  has 
acquired  the  art  of  causing  his  mus- 
cles to  act  in  concert.  Movements 
once  difficult  are  now  carried  on  with 
ease.  The  power  of  coordination  is 
increased,  so  that  a  desired  end  is 
attained  with  the  least  amount  of 
physical  force  and  nervous  energy. 
In  learning  to  row,  play  baseball, 
ride  the  bicycle,  or  in  any  other  exer- 
cises, the  beginner  makes  his  move- 
ments in  a  stiff  and  awkward  manner. 
He  will  use  and  waste  more  muscular 
force  in  playing  one  game  of  ball,  or 
in  riding  a  mile  on  his  wheel,  than  an 
expert  would  in  doing  ten  times  the 
work.  He  has  not  yet  learned  to 
balance  one  set  of  muscles  against 
their  antagonists. 

In  time,  however,  acts  which  were 


FIG.  40.  — The  Standard  Spe- 
cial Chest  Weight. 


A  convenient  machine  by  means 

first  done  only  with  effort  and  by  a       Of  which  ail  the  muscles  of  the 

body  may  be  easily  and  pleas- 
antly exercised  with  sufficient 
variations  in  the  movements  to 
relieve  it  of  monotony. 
A  space  6  ft.  wide,  6  ft.  deep,  and 

is  developed  in  the  spinal  cord  and 
the    muscular    centers 


conscious  will,  become  automatic. 
The  will  ceases  to  concern  itself.  By 
what  is  called  reflex  action,  memory 


7  ft.  high  nearly  in  front  of  the 
machine  is  required  for  exercise." 


(sec.     273). 

There  is  thus  a  great  saving  of  actual  brain  work,  and  one 
important  cause  of  fatigue  is  removed. 


82  PRACTICAL    PHYSIOLOGY. 

83.  Effect  of  Exercise  on  Important  Organs.  The  impor- 
tance of  regular  exercise  is  best  understood  by  noting  its  effects 
upon  the  principal  organs  of  the  body.  As  the  action  of  the 
heart  is  increased  both  in  force  and  frequency  during  exercise, 
the  flow  of  blood  throughout  the  body  is  augmented.  This 
results  from  the  force  of  the  muscular  contractions  which  play 
their  part  in  pressing  the  blood  in  the  veins  onward  towards  the 
heart.  Exercise  also  induces  a  more  vigorous  respiration,  and 
under  increased  breathing  efforts  the  lung  capacity  is  increased 
and  the  size  of  the  chest  is  enlarged.  The  amount  of  air  inspired 
and  expired  in  a  given  time  is  much  larger  than  if  the  body 
were  at  rest.  The  blood  is  thus  supplied  with  a  much  larger 
amount  of  oxygen  from  the  air  inhaled,  and  gives  off  to  the 
air  a  corresponding  excess  of  carbon  dioxid  and  water. 

Again,  exercise  stimulates  and  strengthens  the  organs  of 
digestion.  The  appetite  is  improved,  as  is  especially  noted 
after  exercise  in  the  open  air.  The  digestion  is  more  complete, 
absorption  becomes  more  rapid,  the  peristaltic  movements  of 
the  bowels  are  promoted,  and  the  circulation  through  the  liver 
is  more  vigorous.  More  food  is  taken  to  supply  the  force 
necessary  for  the  maintenance  of  the  mechanical  movements. 
Ample  exercise  also  checks  the  tendency  towards  a  torpid 
circulation  in  the  larger  digestive  organs,  as  the  stomach  and 
the  liver,  so  common  with  those  who  eat  heartily,  but  lead 
sedentary  lives.  In  short,  exercise  may  be  regarded  as  a  great 
regulator  of  nutrition. 

Exercise  increases  the  flow  of  blood  through  the  small  vessels 
of  the  skin,  and  thus  increases  the  radiation  of  heat  from  the 
surface.  If  the  exercise  be  vigorous  and  the  weather  hot,  a 
profuse  sweat  ensues,  the  rapid  evaporation  of  which  cools  the 
body.  The  skin  is  thus  a  most  important  regulator  of  the 
bodily  temperature,  and  prevents  any  rise  above  the  normal 
which  would  otherwise  result  from  vigorous  exercise.  (See 
sees.  226  and  241). 


PHYSICAL    EXERCISE. 


84.  Effect  of  Exercise  upon  the  Personal  Appearance.  Judicious 
and  systematic  exercise,  if  moderately  employed,  soon  gives  a  more 
upright  and  symmetrical  figure,  and  an  easier  and  more  graceful  car- 
riage. Rounded  shoulders  become 
square,  the  awkward  gait  disap- 
pears, and  there  is  seen  a  graceful 
poise  to  the  head  and  a  bearing 
of  the  body  which  mark  those 
whose  muscles  have  been  well 
trained.  A  perfectly  formed  skele- 
ton and  well-developed  muscles 
give  the  graceful  contour  and  per- 
fect outline  to  the  human  body. 
The  lean,  soft  limbs  of  those  who 
have  never  had  any  physical  edu- 
cation, often  look  as  if  they  be- 
longed to  persons  recovering  from 
sickness.  The  effects  of  sound 
physical  exercise  are  well  exhibited 
in  the  aspect  of  the  neck,  shoul- 
ders, and  chest  of  one  who  has 
been  well  trained.  This  is  notice- 
able in  gymnasts  and  others  who 


FIG.  41.  —  Young  Woman  practicing  at 
Home  with  the  "  Whitely  Exerciser." 
(From  a  photograph.) 


practice  upon  the  horizontal  bar, 
with  chest  weights,  dumb-bells, 
and  other  apparatus  which  de- 
velop more  especially  the  muscles  of  the  upper  half  of  the  trunk. 
Exercise  improves  the  condition  of  the  tissues  generally.  They 
become  more  elastic,  and  in  all  respects  sounder.  The  skin  becomes 
firm,  clear,  and  wholesome.  Hence,  every  part  of  the  surface  of 
the  body  rapidly  takes  on  a  change  in  contour,  and  soon  assumes 
that  appearance  of  vigor  and  soundness  which  marks  those  of  firm 
physical  condition.  The  delicate,  ruddy  aspect  of  the  complexion, 
the  swing  about  the  body  and  the  bearing  of  the  head  and  shoulders, 
of  young  women  whose  physical  training  has  been  efficient,  are  in 
marked  contrast  with  those  characteristics  in  persons  whose  educa- 
tion in  this  respect  has  been  neglected. 


84  PRACTICAL    PHYSIOLOGY. 

85.    Effect   of   Unsuitable  or   Excessive  Exercise.      But 

exercise,  like  everything  else  which  contributes  to  our  welfare, 
may  be  carried  to  excess.  The  words  excessive  and  unsuitable, 
when  applied  to  muscular  exertion,  are  relative  terms,  and 
apply  to  the  individual  rather  than  to  amount  of  work  done. 
Thus  what  may  be  excessive  for  one  person,  might  be  suitable 
and  beneficial  to  another.  Then  the  condition  of  the  individual, 
rather  than  the  character  of  the  muscular  work,  is  always  a 
most  important  factor. 

Breathlessness  is,  perhaps,  the  most  common  effect  of  undue 
exertion.  Let  a  middle-aged  person,  who  is  out  of  practice, 
run  a  certain  distance,  and  he  is  soon  troubled  with  his  breath- 
ing. The  respirations  become  irregular,  and  there  is  a  sense 
of  oppression  in  his  chest.  He  pants,  and  his  strength  gives 
out.  His  chest,  and  not  his  legs,  has  failed  him.  He  is  said 
to  be  "  out  of  breath."  He  might  have  practiced  dumb-bells 
or  rowed  for  some  time  without  inconvenience. 

The  heart  is  often  overstrained,  and  at  times  has  been 
ruptured  during  violent  exertion,  as  in  lifting  an  immense 
weight.  The  various  forms  of  heart-disease  are  common  with 
those  whose  occupations  involve  severe  muscular  effort,  as  pro- 
fessional athletes  and  oarsmen.  Haemorrhages  of  various  kinds, 
especially  from  the  lungs,  or  rupture  of  blood-vessels  in  the 
brain,  are  not  uncommon  results  of  over-exertion. 

Excessive  repetition  of  muscular  movements  may  lead  to  per- 
manent contractions  of  the  parts  involved.  Thus  sailors, 
mechanics,  and  others  frequently  develop  a  rigidity  of  the 
tendons  of  the  hand  which  prevents  the  full  extension  of  the 
fingers.  So  stenographers,  telegraphers  and  writers  occasionally 
suffer  from  permanent  contractions  of  certain  muscles  of  the 
arm,  known  as  writer's  cramp,  due  to  their  excessive  use.  But 
the  accidents  which  now  and  then  may  result  from  severe 
physical  exertion,  should  discourage  no  one  from  securing  the 
benefits  which  accrue  from  moderate  and  reasonable  exercise. 


PHYSICAL    EXERCISE.  85 

86.  Muscular  Fatigue.  We  all  know  how  tiresome  it  is  to 
hold  the  arm  outstretched  horizontally  even  for  a  few  moments. 
A  single  muscle,  the  deltoid,  in  this  case  does  most  of  the 
work.  Even  in  a  vigorous  man,  this  muscle  can  act  no  longer 
than  four  to  six  minutes  before  the  arm  drops  helpless.  We 
may  prolong  the  period  by  a  strong  effort  of  the  will,  but  a 


FIG.  42.  —  A  Well-Equipped  Gymnasium. 
(From  a  photograph.) 

time  soon  comes  when  by  no  possible  effort  are  we  able  to  hold 
out  the  arm.  The  muscle  is  said  to  be  fatigued.  It  has  by  no 
means  lost  its  contractile  power,  for  if  we  apply  a  strong  electric 
stimulus  to  it,  the  fatigue  seems  to  disappear.  Thus  we  see 
the  functional  power  of  a  muscle  has  a  definite  limit,  and  in 
fatigue  that  limit  is  reached. 

The  strength  of  the  muscle,  its  physical  condition,  the  work 
it  has  done,  and  the  mental  condition  of   the  individual,  all 


86  PRACTICAL    PHYSIOLOGY. 

modify  the  state  of  fatigue.  In  those  difficult  acts  which 
involve  a  special  effort  of  the  will,  the  matter  of  nerve  exhaus- 
tion is  largely  concerned.  Thus,  the  incessant  movements  in 
St.  Vitus'  dance  result  in  comparatively  little  fatigue,  because 
there  is  no  association  of  the  brain  with  the  muscular  action. 
If  a  strong  man  should  attempt  to  perform  voluntarily  the 
same  movements,  he  would  soon  have  to  rest.  None  of  the 
movements  which  are  performed  independently  of  the  will,  as 
the  heart-beats  and  breathing  movements,  ever  involve  the  sen- 
sation of  fatigue.  As  a  result  of  fatigue  the  normal  irritability 
of  muscular  tissue  becomes  weakened,  and  its  force  of  contract- 
tion  is  lessened.  There  is,  also,  often  noticed  in  fatigue  a 
peculiar  tremor  of  the  muscles,  rendering  their  movements 
uncertain.  The  stiffness  of  the  muscles  which  comes  on  during 
severe  exercise,  or  the  day  after,  are  familiar  results  of  fatigue. 

This  sense  of  fatigue  should  put  us  on  guard  against  danger. 
It  is  a  kind  of  regulator  which  serves  in  the  ordinary  actions 
of  life  to  warn  us  not  to  exceed  the  limits  of  useful  exercise. 
Fatigue  summons  us  to  rest  long  before  all  the  force  of  the 
motor  organs  has  been  expended,  just  as  the  sensation  of 
hunger  warns  us  that  we  need  food,  long  before  the  body  has 
become  weak  from  the  lack  of  nourishment. 

We  should  never  forget  that  it  is  highly  essential  to  maintain 
an  unused  reserve  of  power,  just  as  a  cautious  merchant  always 
keeps  at  the  bank  an  unexpended  balance  of  money.  If  he 
overspends  his  money  he  is  bankrupt,  and  the  person  who  over- 
spends his  strength  is  for  the  time  physically  bankrupt.  In  each 
case  the  process  of  recovery  is  slow  and  painful. 

87.  Rest  for  the  Muscles.  Rest  is  necessary  for  the 
tissues,  that  they  may  repair  the  losses  sustained  by  work; 
that  is,  a  period  of  rest  must  alternate  with  a  period  of  activity. 
Even  the  heart,  beating  ceaselessly,  has  its  periods  of  absolute 
rest  to  alternate  with  those  of  work.  A  steam-engine  is  always 


PHYSICAL    EXERCISE.  / 

slowly,  but  surely,  losing  its  fitness  for  work.  At  last  it  stops 
from  the  need  of  repair.  Unlike  the  engine,  the  body  is  con- 
stantly renewing  itself  and  undergoing  continual  repair.  Were 
it  not  for  this  power  to  repair  and  renew  its  various  tissues,  the 
body  would  soon  be  worn  out. 

This  repair  is  really  a  renovation  of  the  structure.  Rest  and 
work  are  relative  terms,  directly  opposed  to  each  other.  Work 
quickens  the  pulse  and  the  respiration,  while  rest  slows  both. 
During  sleep  the  voluntary  muscles  are  relaxed,  and  those  of 
organic  life  work  with  less  energy.  The  pulse  and  the  respira- 
tion are  less  frequent,  and  the  temperature  lower  than  when 
awake.  Hence  sleep,  "tired  Nature's  sweet  restorer,"  may  be 
regarded  as  a  complete  rest. 

The  periods  of  rest  should  vary  with  the  kind  of  exercise. 
Thus  exercise  which  produces  breathlessness  requires  frequent 
but  short  rests.  The  trained  runner,  finding  his  respiration 
embarrassed,  stops  a  moment  to  regain  his  breath.  Exercises 
of  endurance  cause  fatigue  less  quickly  than  those  of  speed,  but 
require  longer  rest.  Thus  a  man  not  used  to  long  distances 
may  walk  a  number  of  hours  without  stopping,  but  while  fatigue 
is  slow  to  result,  it  is  also  slow  to  disappear.  Hence  a  lengthy 
period  of  rest  is  necessary  before  he  is  able  to  renew  his 
journey. 

88.   Amount  of  Physical  Exercise  Required.    The  amount 

of  physical  exercise  that  can  be  safely  performed  by  each  per- 
son, is  a  most  important  and  practical  question.  No  rule  can 
be  laid  down,  for  what  one  person  bears  well,  may  prove  very 
injurious  to  another.  To  a  certain  extent,  each  must  be  guided 
by  his  own  judgment.  If,  after  taking  exercise,  we  feel  fatigued 
and  irritable,  are  subject  to  headache  and  sleeplessness,  or  find 
it  difficult  to  apply  the  mind  to  its  work,  it  is  plain  that  we  have 
been  taxing  our  strength  unduly,  and  the  warnings  should  be 
heeded. 


88 


PRACTICAL    PHYSIOLOGY. 


Age  is  an  important  factor  in  the  problem,  as  a  young  man 
may  do  with  ease  and  safety,  what  might  be  injurious  to  an 
older  person.  In  youth,  when  the  body  is  making  its  most  active 
development,  the  judicious  use  of  games,  sports,  and  gymnastics 
is  most  beneficial.  In  advanced  life,  both  the  power  and  the 

inclination  for  exercise 
fail,  but  even  then  effort 
should  be  made  to  take 
a  certain  reasonable 
amount  of  exercise. 

Abundant  evidence 
shows  that  physical 
development  is  most 
active  from  thirteen  to 
seventeen  years  of  age  ; 
this  manifests  itself 
clearly  by  increase  in 
weight.  Hence  this 
period  of  life  is  of  great 
consequence.  If  at  this 


FIG.  43.  —  Student  exercising  in  the  School  Gym- 
nasium  on   the    Rowing    Machine, 
photograph.) 


(From  a  age  a  boy  or  girl  is  sub- 
jected to  undue  physi- 
cal strain,  the  development  may  suffer,  the  growth  be  retarded, 
and  the  foundation  laid  for  future  ill  health. 

The  proper  amount  of  exercise  must  vary  greatly  with  circum- 
stances. It  may  be  laid  down  as  a  fairly  safe  rule,  that  a 
person  of  average  height  and  weight,  engaged  in  study  or  in 
any  indoor  or  sedentary  occupation,  should  take  an  amount  of 
exercise  equivalent  to  walking  five  or  six  miles  a  day.  Growing 
children,  as  a  rule,  take  more  exercise  than  this,  while  most  men 
working  indoors  take  far  less,  and  many  women  take  less 
exercise  than  men.  Exercise  may  be  varied  in  many  ways, 
the  more  the  better ;  but  for  the  most  part  it  should  always  be 
taken  in  the  open  air. 


PHYSICAL    EXERCISE.  89 

89.  Time  for  Exercise.     It  is  not  prudent  to  do  hard  work 
or  take  severe  exercise,  just  before  or  just  after  a  full  meal.   The 
best  time  is  one  or  two  hours  after  a  meal.     Vigorous  exercise 
while  the  stomach  is  busily  digesting  food,  may  prove  injurious, 
and  is  apt  to  result  sooner  or  later  in  dyspepsia.     On  the  other 
hand,  severe  exercise  should  not  be  taken  on  an  empty  stomach. 
Those  who  do  much  work  or  study  before  breakfast,  should  first 
take  a  light  lunch,  just  enough  to  prevent  any  faint  feeling. 
With  this  precaution,  there  is  no  better  time  for  moderate  exer- 
cise than  the  early  morning. 

In  the  case  of  children,  physical  exercises  should  not  be 
undertaken  when  they  are  overtired  or  hungry.  Neither  is  it 
judicious  for  adults  to  take  vigorous  exercise  in  the  evening, 
after  a  long  and  arduous  day's  work. 

90.  Walking,  Running,  and  Jumping.      Walking  is  gener- 
ally regarded  as  the  simplest  and  most  convenient  mode  of  tak- 
ing exercise.    Man  is  essentially  a  walking  animal.  When  taken 
with  a  special  object  in  view,  it  is  the  best  and  most  pleasant  of 
all  physical  activities.     It  is  suited  for  individuals  of  all  ages 
and  occupations,  and  for  residents  of  every  climate.    The  child, 
the  athlete,  and  the  aged  are  all  able  to  indulge  in  this  simple 
and  effective  means  of  keeping  the  body  in  health. 

In  walking,  the  muscles  of  the  entire  body  are  brought  into 
action,  and  the  movements  of  breathing  and  the  circulation  of 
the  blood  are  increased.  The  body  should  be  erect,  the  chest 
thrown  out,  the  head  and  shoulders  held  back,  and  the  stride 
long  and  elastic.  It  is  an  excellent  custom  to  add  to  the  use- 
fulness of  this  fine  exercise,  by  deep,  voluntary  inhalations  of 
pure  air. 

Running  is  an  excellent  exercise  for  children  and  young 
people,  but  should  be  sparingly  indulged  in  after  the  age  of 
thirty-five.  If  it  be  accompanied  with  a  feeling  of  faint- 
ness,  breathlessness,  and  palpitation  of  the  heart,  the  exer- 


9O  PRACTICAL    PHYSIOLOGY. 

cise  is  too  severe,  and  its  continuance  may  do  serious  harm. 
Running  as  an  exercise  is  beneficial  to  those  who  have  kept 
themselves  in  practice  and  in  sound  condition.  It  brings  into 
play  nearly  every  muscle  of  the  body,  and  thus  serves  to  de- 
velop the  power  of  endurance,  as  well  as  strength  and  capacity 
for  rapid  movement. 

Jumping  may  well  be  left  to  boys  and  young  men  under 
twenty,  but  skipping  with  a  rope,  allied  to  jumping,  is  an 
admirable  and  beneficial  form  of  exercise.  It  brings  into 
action  many  muscles  without  putting  undue  strain  upon  any 
particular  group. 

91.  Skating,  Swimming,  and  Rowing.  Skating  is  a  de- 
lightful and  invigorating  exercise.  It  calls  into  play  a  great 
variety  of  muscles,  and  is  admirably  adapted  for  almost  all 
ages.  It  strengthens  the  ankles  and  helps  give  an  easy  and 
graceful  carriage  to  the  body.  Skating  is  especially  valuable, 
as  it  can  be  enjoyed  when  other  out-door  exercises  are  not 
convenient. 

Every  child  above  ten  years  of  age  should  be  taught  to 
swim.  The  art,  once  mastered,  is  never  forgotten.  It  calls 
into  use  a  wide  combination  of  muscles.  This  accomplishment, 
so  easily  learned,  should  be  a  part  of  our  education,  as  well  as 
baseball  or  bicycling,  as  it  may  chance  to  any  one  to  save  his 
own  life  or  that  of  a  companion. 

In  many  respects  rowing  is  one  of  the  most  perfect  exercises 
at  our  command.  It  expands  the  chest,  strengthens  the  body, 
and  gives  tone  to  the  muscles  of  the  abdomen.  It  is  very  suit- 
able for  girls  and  women,  as  no  other  exercise  is  so  well  adapted 
to  remedy  the  muscular  defects  so  marked  in  their  sex.  Even 
elderly  persons  can  row  day  after  day  without  difficulty.  The 
degree  of  muscular  effort  required,  can  be  regulated  so  that 
those  with  weak  hearts  and  weak  lungs  can  adjust  them- 
selves to  the  exercise. 


PHYSICAL    EXERCISE.  9 1 

92.  Bicycling  as  an  Exercise.     The  bicycle  as  a  means  of 
taking  exercise   has  come  into  popular  use  with  remarkable 
rapidity.     Sharp  competition  bids  fair  to  make  the  wheel  more 
popular  and  less  expensive  than  ever.     Its  phenomenal  use  by 
persons  of  all  ages  and  in  all  stations  of  life,  is  proof  of  the 
enthusiasm  with  which  this  athletic   exercise  is  employed  by 
women  as  well  as  by  men. 

Mechanical  skill  has  removed  most  of  the  risks  to  health 
and  person  which  once  existed.  A  good  machine,  used  by 
its  owner  with  judgment,  is  the  most  convenient,  the  safest, 
and  the  least  expensive  means  of  traveling  for  pleasure  or 
exercise.  It  is  doing  more  than  any  other  form  of  exercise  to 
improve  the  bodily  condition  of  thousands  whose  occupations 
confine  them  all  day  to  sedentary  work.  Dependent  upon  no 
one  but  himself,  the  cyclist  has  his  means  of"  exercise  always 
at  hand.  No  preparation  is  necessary  to  take  a  spin  of  ten 
miles  or  so  on  the  road,  during  a  summer  evening  or  before 
breakfast. 

Bicycling  brings  into  active  use  the  muscles  of  the  legs  as 
well  as  those  of  the  trunk  and  arms.  It  seems  to  benefit  those 
who  suffer  from  dyspepsia,  constipation,  and  functional  dis- 
orders of  the  liver. 

A  special  caution  must  be  used  against  overdoing  in  cycling, 
for  the  temptation  by  rivalry,  making  a  record,  by  social  com- 
petition on  the  road,  is  stronger  in  this  form  of  exercise  than 
in  any  other,  especially  for  young  folks.  Many  cases  have 
occurred  of  permanent  injury,  and  even  loss  of  life,  from  col- 
lapse simply  by  excessive  exertion  and  exhaustion. 

93.  Outdoor  Games  and  Physical  Education.     While  out- 
door games  are  not  necessary  to  maintain  health,  yet  we  can 
scarcely  overestimate  the  part  that  the  great  games  of  baseball, 
football,  tennis,  golf,  and  croquet,  play  in  the  physical  develop- 
ment of  young  people.     When  played  in  moderation  and  under 


Q2  PRACTICAL    PHYSIOLOGY. 

suitable  conditions,  they  are  most  useful  and  beneficial  exer- 
cises. They  are  played  in  the  open  air,  and  demand  a  great 
variety  of  vigorous  muscular  movement,  with  a  considerable 
amount  of  skill  and  adroitness  of  action.  These  games  not 
only  involve  healthful  exercise,  but  develop  all  those  manly 
and  wholesome  qualities  so  essential  to  success  in  life. 

A  vigorous  body  is  well-nigh  essential  to  success,  but  equally 
important  are  readiness  of  action,  sound  judgment,  good  temper, 
personal  courage,  a  sense  of  fair  play,  and  above  all,  a  spirit  of 
honor.  Outdoor  games,  when  played  in  a  reasonable  and 
honorable  manner,  are  most  efficient  and  practical  means  to 
develop  these  qualities  in  young  people. 


94.  The  School  and  Physical  Education.  The  advantages  to  be 
derived,  during  the  school  period,  from  the  proper  care  and  develop- 
ment of  the  body,  should  be  understood  and  appreciated  by  school 
officials,  teachers,  and  parents..  The  school  period  is  the  best  time 
to  shape  the  lives  of  pupils,  not  mentally  or  morally  alone,  but  physi- 
cally as  well.  This  is  the  time,  by  the  use  of  a  few  daily  exercises  at 
school,  to  draw  back  the  rounding  shoulders,  to  form  the  habit  of 
sitting  and  standing  erect,  to  build  up  strong  and  comely  arms  and 
chests,  and  otherwise  to  train  pupils  to  those  methods  which  will  serve 
to  ripen  them  into  vigorous  and  well-knit  men  and  women. 

Teachers  can  by  a  little  effort  gain  the  knowledge  requisite  prop- 
erly to  instruct  their  pupils  in  a  few  systematic  exercises.  Gratify- 
ing results  will  follow  just  as  the  teacher  and  pupils  evince  interest 
and  judgment  in  the  work.  It  is  found  by  experience  that  pupils  are 
not  only  quick  to  learn,  but  look  forward  eagerly  to  the  physical  exer- 
cises as  an  interesting  change  from  the  routine  of  school  life. 

There  should  be  a  stated  time  for  these  school  exercises,  as  for 
any  other  duty.  There  can  be  practiced  in  the  schoolroom  a  great 
variety  of  interesting  and  useful  exercises,  which  call  for  little  or  no 
expense  for  apparatus.  Such  exercises  should  no  more  interfere  with 
the  children's  usual  games  than  any  other  study  does.  Under  no 
circumstances  should  the  play  hours  be  curtailed. 


PHYSICAL    EXERCISE. 


93 


95.  Physical  Exercises  in  School.  Physical  exercises  of 
some  sort,  then,  should  be  provided  for  pupils  in  our  schools, 
especially  in  large  towns  and  cities,  where  there  is  little  oppor- 
tunity for  outdoor  games,  and  they  should  form  a  part  of  the 
regular  course  of  study.  The  object  should  be  the  promotion 
of  sound  health  rather  than  the  development  of  muscle,  or  per- 
forming feats  of  agility  or  strength.  Exercises  with  dumb-bells 
and  wands,  or  even  without  any  apparatus,  practiced  a  few 


FIG.  44. —  Physical  Exercises  as  carried  on  in  Schools. 
(From  photographs.) 

times  a  day,  for  five  minutes  at  a  time,  do  a  great  deal  of  good. 
They  relax  the  tension  of  body  and  mind,  and  introduce  an 
element  of  pleasure  into  the  routine  of  school  life.  They 
increase  the  breathing  power  and  quicken  the  action  of  the 
heart. 

NOTE.  "  In  early  boyhood  and  youth  nothing  can  replace  the  active  sports  so 
much  enjoyed  at  this  period;  and  while  no  needless  restrictions  should  be  placed 
upon  them,  consideration  should  be  paid  to  the  amount,  and  especially  to  the  charac- 
ter, of  the  games  pursued  by  delicate  youth.  For  these  it  would  be  better  to  develop 
the  weakened  parts  by  means  of  systematic  physical  exercises  and  by  lighter  sports." 
—  DR.  JOHN  M.  KEATING  on  "  Physical  Development  "  in  Pepper's  Cyclopaedia  of 
the  Diseases  of  Children. 


94  PRACTICAL    PHYSIOLOGY. 

If  vigorously  and  systematically  carried  out,  these  exercises 
invigorate  all  the  tissues  and  organs  of  the  body,  and  stimulate 
them  to  renewed  activity.  They  serve  to  offset  the  lack  of  proper 
ventilation,  faulty  positions  at  the  desks,  and  the  prolonged 
inaction  of  the  muscles.  To  secure  the  greatest  benefit  from 
physical  training  in  school,  it  is  important  that  the  pupils  be 
interested  in  these  exercises,  and  consider  them  a  recreation, 
and  not  a  task.1 

96.  Practical  Points  about  Physical  Exercise.  The  main 
object  in  undertaking  systematic  and  graduated  physical  exer- 
cises is  not  to  learn  to  do  mere  feats  of  strength  and  skill,  but 
the  better  to  fit  the  individual  for  the  duties  and  the  work  of  life. 
Exercises  should  be  considered  with  reference  to  their  availa- 
bility from  the  learner's  standpoint.  The  most  beneficial 
exercises  ordinarily  are  the  gentle  ones,  in  which  no  strain  is 
put  upon  the  heart  and  the  respiration.  The  special  aim  is  to 
secure  the  equal  use  of  all  the  muscles,  not  the  development 
of  a  few.  The  performance  of  feats  of  strength  should  never 
come  within  the  scope  of  any  educational  scheme.  Exercises 
which  call  for  sustained  effort,  violent  exertion,  or  sudden 
strain  are  best  avoided  by  those  who  have  had  no  preparation 
or  training. 

Regular  exercise,  not  sudden  and  occasional  prolonged  exer- 
tion, is  necessary  for  health.  The  man  or  woman  who  works 
in  an  office  or  store  all  the  week,  and  on  Sunday  or  a  holiday 
indulges  in  a  long  spin  on  the  bicycle,  often  receives  more  harm 
than  good  from  the  exertion.  Exercise  should  be  taken,  so 

1  "  One-half  the  struggle  of  physical  training  has  been  won  when  a  boy  can  be 
induced  to  take  a  genuine  interest  in  his  bodily  condition,  —  to  want  to  remedy  its 
defects,  and  to  pride  himself  on  the  purity  of  his  skin,  the  firmness  of  his  muscles,  and 
the  uprightness  of  his  figure  Whether  the  young  man  chooses  afterwards  to  use  the 
gymnasium,  to  run,  to  row,  to  play  ball,  or  to  saw  wood,  for  the  purpose  of  improving 
his  physical  condition,  matters  little,  provided  he  accomplishes  that  object."  —  DR. 
D.  A.  SARGENT,  Director  of  the  Hemenway  Gymnasium  at  Harvard  University. 


PHYSICAL    EXERCISE.  95 

far  as  is  convenient,  in  the  open  air,  or  in  a  large  and  well- 
ventilated  room.1 

After  the  more  violent  exercises,  as  baseball,  football,  a  long 
ride  on  the  bicycle,  or  even  after  a  prolonged  walk,  a  warm 
bath  should  be  taken  at  the  first  convenient  opportunity.  Care 
should  be  taken  to  rub  down  thoroughly,  and  to  change  a  part 
or  all  of  the  clothing.  Exercise  is  comparatively  valueless 
until  the  idea  of  taking  it  for  health  is  quite  forgotten  in  the 
interest  and  pleasure  excited  by  the  occasion.  No  exercise 
should  be  carried  to  such  a  degree  as  to  cause  fatigue  or 
exhaustion.  Keep  warmly  clad  after  exercise,  avoid  chills, 
and  always  stop  exercising  as  soon  as  fatigue  is  felt. 

Wear  clothing  which  allows  free  play  to  all  the  muscles  of 
the  body.  The  clothing  should  be  light,  loose,  and  made  of 
wool.  Care  should  be  taken  not  to  take  cold  by  standing  about 
in  clothes  which  are  damp  with  perspiration.  In  brisk  walking 
and  climbing  hills  keep  the  mouth  shut,  especially  in  cold 
weather,  and  breathe  through  the  nose,  regulating  the  pace  so 
that  it  can  be  done  without  discomfort. 

97.  Effect  of  Alcoholic  Liquors  and  Tobacco  upon  Physical 
Culture.  As  a  result  of  the  unusual  attention  given  to  physical 
culture  in  the  last  few  years,  hundreds  of  special  instructors  are 
now  employed  in  training  young  people  in  the  theory  and  prac- 
tice of  physical  exercise.  These  expert  teachers,  to  do  their 
work  with  thoroughness  and  discipline,  recognize  the  necessity 
of  looking  after  the  daily  living  of  their  students.  The  time 
of  rising  and  retiring,  the  hours  of  sleep,  the  dress,  the  care  of 

1  "  It  is  health  rather  than  strength  that  is  the  great  requirement  of  modern  men 
at  modern  occupations ;  it  is  not  the  power  to  travel  great  distances,  carry  great 
burdens,  lift  great  weights,  or  overcome  great  material  obstructions  ;  it  is  simply  that 
condition  of  body,  and  that  amount  of  vital  capacity,  which  shall  enable  each  man  in 
his  place  to  pursue  his  calling,  and  work  on  in  his  working  life,  with  the  greatest 
amount  of  comfort  to  himself  and  usefulness  to  his  fellowmen."  —  MACLAREN'S 
Physical  Education. 


96  PRACTICAL    PHYSIOLOGY. 

the  diet,  and  many  other  details  of  personal  health  become  an 
important  part  of  the  training. 

Recognizing  the  fact  that  alcoholic  drink  and  tobacco  are  so 
disastrous  to  efficiency  in  any  system  of  physical  training,  these 
instructors  rigidly  forbid  the  use  of  these  drugs  under  all  cir- 
cumstances. While  this  principle  is  perhaps  more  rigorously 
enforced  in  training  for  athletic  contests,  it  applies  equally  to 
those  who  have  in  view  only  the  maintenance  of  health. 

Books  on  Physical  Education.  There  are  many  excellent  books  on  physical 
education,  which  are  easily  obtained  for  reading  or  for  reference.  Among  these 
one  of  the  most  useful  and  suggestive  is  Blackie's  well-known  book,  "  How  to  Get 
Strong  and  how  to  Stay  so."  This  little  book  is  full  of  kindly  advice  and  practical 
suggestions  to  those  who  may  wish  to  begin  to  practice  health  exercises  at  home 
with  inexpensive  apparatus.  For  more  advanced  work,  Lagrange's  "  Physiology  of 
Bodily  Exercise  "  and  the  Introduction  to  Maclaren's  "  Physical  Education  "  may  be 
consulted.  A  notable  article  on  "  Physical  Training •'  by  Joseph  H.  Sears,  an  Ex- 
Captain  of  the  Harvard  Football  Team,  may  be  found  in  Roosevelt's  "  In  Sickness 
and  in  Health." 

Price  lists  and  catalogues  of  all  kinds  of  gymnastic  apparatus  are  easily  obtained 
on  application  to  firms  handling  such  goods. 

Various  Systems  of  Physical  Exercises.  The  recent  revival  of  popular  interest 
in  physical  education  has  done  much  to  call  the  attention  of  the  public  to  the  use- 
fulness and  importance  of  a  more  thorough  and  systematic  use  of  physical  exercises, 
both  at  home  and  in  the  schools.  It  is  not  within  the  scope  of  this  book  to  describe 
the  various  systems  of  gymnastic  and  calisthenic  exercises  now  in  common  use  in  this 
country.  For  the  most  part  they  have  been  modified  and  rearranged  from  other 
sources,  notably  from  the  two  great  systems,  i.e.,  Swedish  and  German. 

For  a  most  comprehensive  work  on  the  Swedish  system,  the  teacher  is  referred  to 
the  "  Swedish  System  of  Educational  Gymnastics,"  with  264  illustrations,  by  Baron 
Nils  Posse.  There  is  also  a  small  manual  for  teachers,  called  "  Handbook  of 
School  Gymnastics  of  the  Swedish  Systems,"  by  the  same  author. 


CHAPTER   V. 
FOOD    AND    DRINK. 

98.  Why  we  need  Food.     The  body  is  often  compared  to  a 
steam-engine  in  good  working  order.     An  engine  uses  up  fuel 
and  water  to  obtain  from  them  the  energy  necessary  to  do  its 
work.     So,  we  consume  within  our  bodies  certain    nutritious 
substances  to  obtain  from  them  the  energy  necessary  for  our 
activities.     Just  as  the  energy  for  the  working  of  the  engine  is 
obtained  from  steam  by  the  combustion  of  fuel,  so  the  energy 
possessed  by  our  bodies  results  from  the  combustion  or  oxida- 
tion  within   us  of   the  food  we  eat.     Unless  this  energy  is 
provided  for  the  body  it  will  have  but  little   power  of  doing 
work,  and  like  an   engine  without  steam,  must  soon  become 
motionless. 

99.  Waste   and  Repair.     A    steam-engine   from   the   first 
stroke  of  its  piston-rod  begins  to  wear  out,  and  before  long 
needs  repair.      All  work  involves  waste.      The  engine,  unless 
kept  in  thorough  repair,  would  soon  stop.     So  with  our  bodies. 
In  their  living  cells  chemical  changes  are  constantly  going  on  ; 
energy,  on  the  whole,  is  running  down ;  complex  substances  are 
being  broken  up  into  simpler  combinations.     So  long  as  life 
lasts,  food  must  be  brought  to  the  tissues,  and  waste  products 
carried  away  from  them.      It    is  impossible  to  move  a  single 
muscle,  or  even  to  think  for  one  moment,  without  some  minute 
part  of  the  muscular  or  brain  tissue  becoming  of  no  further 
use  in  the  body.     The  transformation  of  dead  matter  into  living 
tissue  is  the  ever-present  miracle  which  life  presents  even  in  its 
lowest  forms. 


98  PRACTICAL    PHYSIOLOGY. 

In  childhood  the  waste  is  small,  and  the  amount  of  food 
taken  is  more  than  sufficient  to  repair  th'e  loss.  Some  of  the 
extra  food  is  used  in  building  up  the  body,  especially  the 
muscles.  As  we  shall  learn  in  Chapter  VIII.,  food  is  also 
required  to  maintain  the  bodily  heat.  Food,  then,  is  necessary 
for  the  production  of  energy,  for  the  repair  of  the  body,  for  the 
building  up  of  the  tissues,  and  for  the  maintenance  of  bodily 
heat. 

100.  Nature  of  the  Waste  Material.  An  ordinarily  healthy 
person  passes  daily,  on  an  average,  by  the  kidneys  about  50 
ounces  of  waste  material,  of  which  96  per  cent  is  water,  and 
from  the  intestines,  on  an  average,  5  ^  ounces,  a  large  propor- 
tion of  which  is  water.  By  the  skin,  in  the  shape  of  sweat 
and  insensible  perspiration,  there  is  cast  out  about  23  ounces, 
of  which  99  per  cent  is  water  ;  and  by  the  lungs  about  34 
ounces,  10  of  which  are  water  and  the  remainder  carbon 
dioxid. 

Now  if  we  omit  an  estimate  of  the  undigestible  remains  of 
the  food,  we  find  that  the  main  bulk  of  what  daily  leaves  the 
body  consists  of  water,  carbon  dioxid,  and  certain  solid  matters 
contained  in  solution  in  the  renal  secretion  and  the  sweat. 
The  chief  of  these  solid  matters  is  urea,  a  complex  product 
made  up  of  four  elements,  —  carbon,  hydrogen,  oxygen,  and  nitro- 
gen. Water  contains  only  two  elements,  hydrogen  and  oxygen ; 
and  carbon  dioxid  also  has  only  two,  carbon  and  oxygen. 
Hence,  what  we  daily  cast  out  of  our  bodies  consists  essentially 
of  these  four  elements  in  the  form  mainly  of  water,  carbon 
dioxid,  and  urea. 

These  waste  products  represent  the  oxidation  that  has  taken 
place  in  the  tissues  in  producing  the  energy  necessary  for  the 
bodily  activities,  just  as  the  smoke,  ashes,  clinkers,  and  steam 
represent  the  consumption  of  fuel  and  water  in  the  engine. 
Plainly,  therefore,  if  we  could  restore  to  the  body  a  supply  of 


FOOD    AND    DRINK.  99 

these  four  elements  equivalent  to  that  cast  out,  we  could  make 
up  for  the  waste.  The  object  of  food,  then,  is  to  restore  to  the 
body  an  amount  of  the  four  elements  equal  to  that  consumed. 
In  other  words,  and  briefly:  The  purpose  of  food  is  to 
supply  the  waste  of  the  tissues  and  to  maintain  the  normal 
composition  of  the  blood. 

101.  Classification  of  Foods.      Foods  may  be  conveniently 
divided  into  four  great  classes,  to  which  the  name  f ood-stuffs 
or  alimentary  principles  has  been  given.     They  correspond  to 
the  chief  "  proximate  principles  "  of  which  the  body  consists. 
To  one  or  the  other  of  these  classes  all  available  foods  belong.1 
The  classification  of  food-stuffs  usually  given  is  as  follows  : 

I.  Proteids,  or  Nitrogenous  Foods. 

II.  Starches  and  Sugars,  or  Carbohydrates. 

III.  Fats  and  Oils.        . 

IV.  Inorganic  or  Mineral  Foods,  —  Water,  Salt. 

102.  Proteids,  or  Nitrogenous  Foods.     The  proteids,  fre- 
quently spoken  of  as  the  nitrogenous  foods,  are  rich  in  one  or 
more  of  the  following   organic  substances :    albumen,  casein, 
fibrin,  gelatine,  myosin,  gluten,  and  legumin. 

The  type  of  this  class  of  foods  is  albumen,  well  known  as  the 
white  of  an  egg.  The  serum  of  the  blood  is  very  rich  in  albu- 
men, as  is  lean  meat.  The  curd  of  milk  consists  mainly  of 
casein.  Fibrin  exists  largely  in  blood  and  flesh  foods.  Gela- 
tine is  obtained  from  the  animal  parts  of  bones  and  connective 
tissue  by  prolonged  boiling.  One  of  the  chief  constituents  of 

*To  this  classification  may  be  added  what  are  called  albuminoids,  a  group 
of  bodies  resembling  proteids,  but  having  in  some  respects  a  different  nutritive 
value.  Gelatine,  such  as  is  found  in  soups  or  table  gelatine  is  a  familiar  example  of 
the  albuminoids.  They  are  not  found  to  any  important  extent  in  our  raw  foods,  and 
do  not  therefore  usually  appear  in  the  analyses  of  the  composition  of  foods.  The 
albuminoids  closely  resemble  the  proteids,  but  cannot  be  used  like  them  to  build  up 
protoplasm. 


IOO  PRACTICAL  PHYSIOLOGY. 

muscular  fiber  is  myosin.  Gluten  exists  largely  in  the  cereals 
wheat,  barley,  oats,  and  rye.  The  proteid  principle  of  peas  and 
beans  is  legumin,  a  substance  resembling  casein. 

As  the  name  implies,  the  proteids,  or  nitrogenous  foods,  con- 
tain nitrogen ;  carbohydrates  and  fats,  on  the  contrary,  do  not 
contain  nitrogen.  The  principal  proteid  food-stuffs  are  milk, 
eggs,  flesh  foods  of  all  kinds,  fish,  and  the  cereals  among  vege- 
table foods.  Peas  and  beans  are  rich  in  proteids.  The  essen- 
tial use  of  the  proteids  to  the  tissues  is  to  supply  the  material 
from  which  the  new  proteid  tissue  is  made  or  the  old  proteid 
tissue  is  repaired.  They  are  also  valuable  as  sources  of  energy  to 
the  body.  Now,  as  the  proteid  part  of  its  molecule  is  the  most 
important  constituent  of  living  matter,  it  is  evident  that  proteid 
food  is  an  absolute  necessity.  If  our  diet  contained  no  proteids, 
the  tissues  of  the  body  would  gradually  waste  away,  and  death 
from  starvation  would  result.  All  the  food-stuffs  are  necessary 
in  one  way  or  another  to  the  preservation  of  perfect  health,  but 
proteids,  together  with  a  certain  proportion  of  water  and  inor- 
ganic salts,  are  absolutely  necessary  for  the  bare  maintenance 
of  animal  life  —  that  is,  for  the  formation  and  preservation  of 
living  protoplasm. 

103.  Starches  and  Sugars.  The  starches,  sugars,  and 
gums,  also  known  as  carbohydrates,  enter  largely  into  the 
composition  of  foods  of  vegetable  origin.  They  contain  no 
nitrogen,  but  the  three  elements,  carbon,  hydrogen,  and  oxygen, 
the  last  two  in  the  same  proportion  as  in  water.  The  starches 
are  widely  distributed  throughout  the  vegetable  kingdom.  They 
are  abundant  in  potatoes  and  the  cereals,  and  in  arrowroot, 
rice,  sago,  and  tapioca.  Starch  probably  stands  first  in  impor- 
tance among  the  various  vegetable  foods. 

The  sugars  are  also  widely  distributed  substances,  and 
include  the  cane,  grape,  malt,  maple,  and  milk  sugars.  Here 
also  belong  the  gums  and  cellulose  found  in  fruit,  cereals,  and  all 


FOOD    AND    DRINK.  JIOI 

vegetables  which  form  the  basis  of  the  plant  cells  and  fibers. 
Honey,  molasses,  and  manna  are  included  in  this  class. 

The  physiological  value  of  the  starches  and  sugars  lies  in  the 
fact  that  they  are  oxidized  in  the  body,  and  a  certain  amount 
of  energy  is  thereby  liberated.  The  energy  of  muscular  work 
and  of  the  heat  of  the  body  comes  largely  from  the  oxidation, 
or  destruction,  of  this  class  of  foods.  Now,  inasmuch  as  we 
are  continually  giving  off  energy  from  the  body,  chiefly  in  the 
form  of  muscular  work  and  heat,  it  is  evident  that  material  for 
the  production  of  this  energy  must  be  taken  in  the  food.  The 
carbohydrates  constitute  the  bulk  of  our  ordinary  food. 

104.  Fats  and  Oils.  These  include  not  only  the  ordinary 
fats  of  meat,  but  many  animal  and  vegetable  oils.  They  are 
alike  in  chemical  composition,  consisting  of  carbon  and  hydro- 
gen, with  a  little  oxygen  and  no  nitrogen.  The  principal  kinds 
of  fat  used  as  food  are  the  fat  of  meat,  butter,  suet,  and  lard ; 
but  in  many  parts  of  the  world  various  vegetable  oils  are 
largely  used,  as  the  olive,  palm,  cotton  seed,  cocoanut,  and 
almond. 

The  use  of  the  fats  in  the  body  is  essentially  the  same  as  that 
of  the  starches  and  sugars.  Weight  for  weight  they  are  more 
valuable  than  the  carbohydrates  as  sources  of  energy,  but  the 
latter  are  more  easily  digested,  and  more  easily  oxidized  in  the 
body.  An  important  use  of  fatty  foods  is  for  the  maintenance 
of  the  bodily  heat.  The  inhabitants  of  Arctic  regions  are  thus 
enabled,  by  large  use  of  the  fat  and  oil  from  the  animals  they 
devour,  to  endure  safely  the  severe  cold.  Then  there  is  reason 
to  believe  that  fat  helps  the  digestion  of  other  foods,  for  it  is 
found  that  the  body  is  better  nourished  when  the  fats  are  used 
as  food.  When  more  fat  is  consumed  than  is  required  to  keep 
up  the  bodily  heat  and  to  yield  working  power,  the  excess  is 
stored  up  in  various  parts  of  the  body,  making  a  sort  of  reserve 
fuel,  which  may  be  drawn  upon  at  any  future  time. 


IO2 


PRA'CTlCAL    PHYSIOLOGY. 


105.  Saline  or  Mineral  Foods.      All  food  contains,  besides 
the  substances  having  potential  energy,  as  described,  certain 
saline  matters.     Water  and  salts  are  not  usually  considered 
foods,   but   the  results  of    scientific  research,    as  well   as   the 
experience  of  life,  show  that  these  substances  are  absolutely 
necessary  to  the  body.     The  principal  mineral  foods  are  salt, 
lime,  iron,  magnesia,  phosphorus,  potash,  and  water.       Except 
common  salt  and  water,  these  substances  are  usually  taken  only 
in  combination  with  other  foods. 

These  saline  matters  are  essential  to  health,  and  when  not 
present  in  due  proportion  nutrition  is  disturbed.  If  a  dog  be 
fed  on  food  freed  from  all  salines,  but  otherwise  containing 
proper  nutrients,  he  soon  suffers  from  weakness,  after  a  time 
amounting  to  paralysis,  and  often  dies  in  convulsions. 

About  200  grains  of  common  salt  are  required  daily  by  an 
adult,  but  a  large  proportion  of  this  is  in  our  food.  Phosphate 
of  lime  is  obtained  from  milk  and  meats,  and  carbonate  of  lime 
from  the  hard  water  we  drink.  Both  are  required  for  the  bones 
and  teeth.  The  salts  of  potash,  which  assist  in  purifying  the 
blood,  are  obtained  from  vegetables  and  fruits.  An  iron  salt  is 
found  in  most  foods,  and  sulphur  in  the  yolk  of  eggs. 

106.  Water.     Water  is  of    use    chiefly  as  a  solvent,  and 
while  not  strictly  a  food,  is  necessary  to  life.     It  enters  into  the 
construction  of  every  tissue  and  is  constantly  being  removed 
from  the  body  by  every  channel  of  waste.1 

1  The  amount  of  water  in  various  tissues  of  the  body  is  given  by  the  following 
table  in  parts  of  1000: 


SOLIDS. 


Enamel, 

Dentine, 

Bone, 

Fat, 

Cartilage, 

Liver, 

Skin, 


486 
299 
55° 
693 
720 


Brain, 
Muscle, 
Spleen, 
Kidney, 
Vitreous  hu- 
mor, 


LIQUIDS. 

750 

Blood, 

79  i 

Serum, 

959 

757 

Bile, 

864 

Gastric  juice, 

973 

758 

Blood  plasma, 

901 

Tears, 

982 

827 

Chyle, 

928 

Saliva, 

995 

Lymph, 

958 

Sweat, 

995 

987 

FOOD    AND    DRINK. 


103 


As  a  solvent  water  aids  digestion,  and  as  it  forms  about  80 
per  cent  of  the  blood,  it  serves  as  a  carrier  of  nutrient  material 
to  all  the  tissues  of  the  body. 


IMPORTANT   ARTICLES    OF   DIET. 

107.  Milk.  The  value  of  milk  as  a  food  cannot  be  over- 
estimated. It  affords  nourishment  in  a  very  simple,  convenient, 
and  perfect  form.  It  is  the  sole  food  provided  for  the  young  of 
all  animals  which  nourish  their  young.  It  is  an  ideal  food 
containing,  in  excellent  proportions,  all  the  four  elements  neces- 
sary for  growth  and  health  in  earlier  youth. 

Cheese  is  the  nitrogenous  part  of  milk,  which  has  been 
coagulated  by  the  use  of  rennet.  The  curd  is  then  carefully 

Composition  of  Food  Materials.  Careful  analyses  have  been  made  of  the  dif- 
ferent articles  of  food,  mostly  of  the  raw,  or  uncooked  foods.  As  might  be  expected, 
the  analyses  on  record  differ  more  or  less  in  the  percentages  assigned  to  the  various 
constituents,  but  the  following  table  will  give  a  fair  idea  of  the  fundamental  nutritive 
value  of  the  more  common  foods  : 


In  100  parts 

Water 

Proteid 

Fat 

Carbohydrate 

Ash 

Digestible 

Cellulose 

Meat  

76.7 

20.8 

1.5 

0.3 

1.7 

EsrcrS 

73   7 

12.6 

12.  1 

Cheese    

/J'/ 

36-60 

25-33 

7-30 

3-7 

— 

3-4 

Cow's  Milk     .     .     . 

87.7 

3-4 

3-2 

4.8 

— 

0.7 

Wheat  Flour  ....    . 

13-3 

10.2 

0.9 

74.8 

0.3 

o-S 

Wheat  Bread  .-...-'  . 

35-6 

7-i 

0.2 

55-5 

0.3 

i.i 

Rye  Flour  .... 

13-7 

"•5 

2.1 

69.7 

1.6 

M 

Rye  bread  .... 

42-3 

6.1 

0.4 

49.2 

0.5 

1-5 

Rice   ...... 

J3-1 

7.0 

O.g 

77-4 

0.6 

I.O 

Corn  

X3-  ' 

9-9 

4.6 

68.4 

2  e 

T     C 

Macaroni     .... 

10.  I 

9.0 

0-3 

79.0 

**3 

0.3 

••a 
0-5 

Peas  and  Beans  .     . 

12-15 

23-26 

«H 

49-54 

4-7 

2-3 

Potatoes      .... 

75-5 

2.0 

0.2 

20.6 

0.7 

I.O 

Carrots   .          ... 

87.1 

I.O 

O.2 

Q   1 

I    A 

Cabbage  

90 

2-3 

o-5 

?'6 

4-6 

1.4 

1-2 

0.9 

'•3 

Fruit 

84 

0.5 

— 

10 

4 

0.5 

IO4  PRACTICAL    PHYSIOLOGY. 

dried,  salted,  and  pressed.  Cheese  is  sometimes  difficult  of 
digestion,  as  on  account  of  its  solid  form  it  is  not  easily  acted 
upon  by  the  digestive  fluids. 

108.  Meats.     The    flesh    of    animals    is   one   of  our  main 
sources  of  food.      Containing  a  large  amount   of   proteid,   it 
is  admirably  adapted  for  building  up  and  repairing  the  tissues 
of  the  body.     The  proportion  of  water  is  also  high,  varying 
from  50  to  75  per  cent.    The  most  common  meats  used  in  this 
country  are  beef,  mutton,  veal,  pork,  poultry,  and  game. 

Beef  contains  less  fat  and  is  more  nutritious  than  either 
mutton  or  pork.  Mutton  has  a  fine  flavor  and  is  easily  digested. 
Veal  and  lamb,  though  more  tender,  are  less  easily  digested. 
Pork  contains  much  fat,  and  its  fiber  is  hard,  so  that  it  is  the 
most  difficult  to  digest  of  all  the  meats.  Poultry  and  game 
have  usually  a  small  proportion  of  fat,  but  are  rich  in  phosphates 
and  are  valued  for  their  flavor. 

109.  Eggs.     Consisting  of  about  two-thirds  water  and  the 
rest  albumen  and  fat,  eggs  are  often  spoken  of  as  typical  natu- 
ral food.     The  white  of  an  egg  is  chiefly  albumen,  with  traces 
of  fat  and  salt ;  the  yolk  is  largely  fat  and  salts.     The  yellow 
color  is  due  partly  to  sulphur.  It  is  this  which  blackens  a  silver 
spoon.     Eggs  furnish  a  convenient  and  concentrated  food,  and 
if  properly  cooked  are  readily  digested. 

HO.  Fish.  Fish  forms  an  important  and  a  most  nutritious 
article  of  diet,  as  it  contains  almost  as  much  nourishment  as 
butcher's  meat.  The  fish- eating  races  and  classes  are  remark- 
ably strong  and  healthy.  Fish  is  less  stimulating  than  meat, 
and  is  thus  valuable  as  a  food  for  invalids  and  dyspeptics.  To 
be  at  its  best,  fish  should  be  eaten  in  its  season.  As  a  rule  shell- 
fish, except  oysters,  are  not  very  digestible.  Some  persons  are 
unable  to  eat  certain  kinds  of  fish,  especially  shell-fish,  without 
eruptions  on  the  skin  and  other  symptoms  of  mild  poisoning. 


FOOD    AND    DRINK.  10$ 

in.  Vegetable  Foods.  This  is  a  large  and  important  group 
of  foods,  and  embraces  a  remarkable  number  of  different  kinds 
of  diet.  Vegetable  foods  include  the  cereals,  garden  vege- 
tables, the  fruits,  and  other  less  important  articles.  These 
foods  supply  a  certain  quantity  of  albumen  and  fat,  but  their 
chief  use  is  to  furnish  starches,  sugars,  acids,  and  salts.  The 
vegetable  foods  indirectly  supply  the  body  with  a  large  amount 
of  water,  which  they  absorb  in  cooking. 

112.  Proteid  Vegetable  Foods.  The  most  important  proteid 
vegetable  foods  are  those  derived  from  the  grains  of  cereals 
and  certain  leguminous  seeds,  as  peas  and  beans.  The  grains 
when  ground  make  the  various  flours  or  meals.  They  contain 
a  large  quantity  of  starch,  a  proteid  substance  peculiar  to  them 
called  gluten,  and  mineral  salts,  especially  phosphate  of  lime. 
Peas  and  beans  contain  a  smaller  proportion  of  starch,  but  more 
proteid  matter,  called  legumin,  or  vegetable  casein.  Of  the 
cereal  foods,  wheat  is  that  most  generally  useful.  Wheat,  and 
corn  and  oatmeal  form  most  important  articles  of  diet.  Wheat 
flour  has  starch,  sugar,  and  gluten  —  nearly  everything  to 
support  life  except  fat. 

Oatmeal  is  rich  in  proteids.  In  some  countries,  as  Scotland, 
it  forms  an  important  article  of  diet,  in  the  form  of  porridge 
or  oatmeal  cakes. 

Corn  meal  is  not  only  rich  in  nitrogen,  but  the  proportion  of 
fat  is  also  large;  hence  it  is  a  most  important  and  nutritious 
article  of  food.  Rice,  on  the  other  hand,  contains  less  proteids 
than  any  other  cereal  grain,  and  is  the  least  nutritious.  Where 
used  as  a  staple  article  of  food,  as  in  India,  it  is  commonly 
mixed  with  milk,  cheese,  or  other  nutritious  substances.  Peas 
and  beans,  distinguished  from  all  other  vegetables  by  their  large 
amount  of  proteids  —  excel  in  this  respect  even  beef,  mutton, 
and  fish.  They  take  the  place  of  meats  with  those  who  believe 
in  a  vegetable  diet. 


IO6  PRACTICAL  PHYSIOLOGY. 

113.  Non-proteid  Vegetable  Foods.  The  common  potato  is 
the  best  type  of  non-proteid  vegetable  food.  When  properly 
cooked  it  is  easily  digested  and  makes  an  excellent  food.  It  con- 
tains about  75  per  cent  of  water,  about  20  per  cent  of  carbohy- 
drates, chiefly  starch,  2  per  cent  of  proteids,  and  a  little  fat  and 
saline  matters.  But  being  deficient  in  flesh-forming  materials, 
it  is  unfit  for  an  exclusive  food,  but  is  best  used  with  milk,  meat, 
and  other  foods  richer  in  proteid  substances.  Sweet  potatoes, 
of  late  years  extensively  used  as  food,  are  rich  in  starch  and 
sugar.  Arrowroot,  sago,  tapioca,  and  similar  foods  are  nutri- 
tious, and  easily  digested,  and  with  milk  furnish  excellent 
articles  of  diet,  especially  for  invalids  and  children. 

Explanation  of  the  Graphic  Chart.  The  graphic  chart,  on  the  next 
page,  presents  in  a  succinct  and  easily  understood  form  the  composition 
of  food  materials  as  they  are  bought  in  the  market,  including  the 
edible  and  non-edible  portions.  It  has  been  condensed  from  Dr.  W. 
O.  Atwater's  valuable  monograph  on  "  Foods  and  Diet."  This  work 
is  known  as  the  Yearbook  of  the  U.  S.  Department  of  Agriculture 
for  1894. 

KEY  :  I,  percentage  of  nutrients ;  2,  fuel  value  of  i  pound  in  calories.  The  unit 
of  heat,  called  a  calorie,  or  gramme-degree,  is  the  amount  of  heat  which  is 
necessary  to  raise  one  gramme  (1543  grains)  of  water  one  degree  centigrade 
(1.8°  Fahr.).  A,  round  beef;  B,  sirloin  beef;  C,  rib  beef;  D,  leg  of  mutton; 
E,  spare  rib  of  pork;  F,  salt  pork;  G,  smoked  ham;  H,  fresh  codfish;  I, 
oysters;  J,  milk;  K,  butter;  L,  cheese;  M,  eggs;  N,  wheat  bread;  O,  corn 
meal;  P,  oatmeal;  Q,  dried  beans;  R,  rice;  S,  potatoes;  T,  sugar. 

This  table,  among  other  things,  shows  that  the  flesh  of  fish  contains 
more  water  than  that  of  warm-blooded  animals.  It  may  also  be  seen 
that  animal  foods  contain  the  most  water  ;  and  vegetable  foods, 
except  potatoes,  the  most  nutrients.  Proteids  and  fats  exist  only  in 
small  proportions  in  most  vegetables,  except  beans  and  oatmeal. 
Vegetable  foods  are  rich  in  carbohydrates  while  meats  contain  none. 
The  fatter  the  meat  the  less  the  amount  of  water.  Thus  very  lean 
meat  may  be  almost  four-fifths  water,  and  fat  pork  almost  one-tenth 
water. 


FOOD    AND    DRINK. 


COMPOSITION  OF  FOOD  MATERIALS. 

Nutritive  ingredients,  refuse,  and  fuel  value. 

Nutrients.  Non-Nutrients. 


Protein.          Fats.  Carbo-        Mineral 

hydrates,      matters. 


Water.         Refuse. 


Fuel  Value. 
Calories. 


90         100 


10 


40 


50 


80 


70 


80 


400         800         1200       1600       2000       2400        2800       3200       3600 


FIG.  45. —  Graphic  Chart  of  the  Composition  of  Food  Materials. 


108  PRACTICAL    PHYSIOLOGY. 

114.  Non-proteid  Animal  Foods.     Butter  is  one  of  the  most 
digestible  of  animal  fats,  agreeable  and  delicate  in  flavor,  and 
is  on  this  account  much  used  as  a  wholesome  food.     Various 
substitutes  have  recently  come  into  use.     These  are  all  made 
from  animal  fat,  chiefly  that  of  beef,  and  are  known  as  butter- 
ine,  oleomargarine,  and  by  other  trade  names.    These  prepara- 
tions, if  properly  made,  are  wholesome,  and  may  be  useful 
substitutes   for    butter,  from  which    they  differ  but   little   in 
composition. 

115.  Garden  Vegetables.     Various  green,  fresh,  and  succu- 
lent vegetables  form  an  essential  part  of  our  diet.     They  are 
of  importance  not  so  much  on  account  of  their  nutritious  ele- 
ments, which  are  usually  small,  as  for  the  salts  they  supply, 
especially  the  salts  of  potash.     It  is  a  well-known  fact  that  the 
continued  use  of  a  diet  from  which  fresh  vegetables  are  excluded 
leads  to  a  disease  known  as  scurvy.     They  are  also  used  for 
the  agreeable    flavor   possessed   by  many,   and   the    pleasant 
variety  and  relish  they  give  to  the  food.     The  undigested  resi- 
due left  by  all  green  vegetables  affords  a  useful  stimulus  to 
intestinal  contraction,  and  tends  to  promote  the  regular  action 
of  the  bowels. 

116.  Fruits.    A  great  variety  of  fruits,  both  fresh  and  dry, 
is  used  as  food,  or  as  luxuries.     They  are  of  little  nutritive 
value,  containing,   as  they  do,  much  water  and  only  a  small 
amount  of  proteid,  but  are  of  use  chiefly  for  the  sugar,  vege- 
table acids,  and  salts  they  contain. 

In  moderate  quantity,  fruits  are  a  useful  addition  to  our  regu- 
lar diet.  They  are  cooling  and  refreshing,  of  agreeable  flavor, 
and  tend  to  prevent  constipation.  Their  flavor  and  juiciness 
serve  to  stimulate  a  weak  appetite  and  to  give  variety  to  an 
otherwise  heavy  diet.  If  eaten  in  excess,  especially  in  an 
unripe  or  an  overripe  state,  fruits  may  occasion  a  disturbance 
of  the  stomach  and  bowels,  often  of  a  severe  form. 


FOOD    AND    DRINK.  IOQ 

117.  Condiments.      The  refinements  of  cookery  as  well  as 
the  craving  of  the  appetite,  demand  many  articles  which  cannot 
be  classed  strictly  as  foods.     They  are  called  condiments,  and 
as  such  may  be  used  in  moderation.     They  give  flavor   and 
relish  to  food,  excite  appetite  and  promote  digestion.     Condi- 
ments increase  the  pleasure  of  eating,  and  by  their  stimulating 
properties  promote  secretions  of  the  digestive  fluids  and  excite 
the  muscular  contractions  of  the  alimentary  canal. 

The  well-known  condiments  are  salt,  vinegar,  pepper,  ginger, 
nutmeg,  cloves,  and  various  substances  containing  ethereal 
oils  and  aromatics.  Their  excessive  use  is  calculated  to  excite 
irritation  and  disorder  of  the  digestive  organs. 

118.  Salt.     The  most  important  and  extensively  used  of  the 
condiments  is  common   salt.     It  exists  in  all  ordinary  articles 
of   diet,  but    in    quantities    not   sufficient  to  meet   the  wants 
of  the  bodily  tissues.     Hence  it  is  added  to  many  articles  of 
food.      It  improves   their  flavor,   promotes   certain   digestive 
secretions,  and  meets  the  nutritive  demands  of  the  body.     The 
use  of  salt  seems  based  upon  an  instinctive  demand  of  the  sys- 
tem for  something  necessary  for  the  full  performance  of  its 
functions.      Food   without   salt,   however    nutritious    in    other 
respects,  is  taken  with  reluctance  and  digested  with  difficulty. 

Salt  has  always  played  an  important  and  picturesque  part  in 
the  history  of  dietetics.  Reference  to  its  worth  and  necessity 
abounds  in  sacred  and  profane  history.  In  ancient  times,  salt 
was  the  first  thing  placed  on  the  table  and  the  last  removed. 
The  place  at  the  long  table,  above  or  below  the  salt,  indicated 
rank.  It  was  everywhere  the  emblem  of  hospitality.  In  parts 
of  Africa  it  is  so  scarce  that  it  is  worth  its  weight  in  gold,  and  is 
actually  used  as  money.  Torture  was  inflicted  upon  prisoners  of 
state  in  olden  times  by  limiting  the  food  to  water  and  bread,  with- 
out salt.  So  intense  may  this  craving  for  salt  become,  that  men 
have  often  risked  their  liberty  and  even  their  lives  to  obtain  it. 


IIO  PRACTICAL  PHYSIOLOGY. 

119.  Water.     The  most  important  natural  beverage  is  pure 
water ;  in  fact  it  is  the  only  one  required.     Man  has,  however, 
from  the  earliest  times  preferred  and  daily  used  a  variety  of 
artificial  drinks,  among  which  are  tea,  coffee,  and  cocoa. 

All  beverages  except  certain  strong  alcoholic  liquors,  consist 
almost  entirely  of  water.  It  is  a  large  element  of  solid  foods, 
and  our  bodies  are  made  up  to  a  great  extent  of  water.  Every- 
thing taken  into  the  circulating  fluids  of  the  body,  or  eliminated 
from  them,  is  done  through  the  agency  of  water.  As  a  solvent 
it  is  indispensable  in  all  the  activities  of  the  body. 

It  has  been  estimated  that  an  average-sized  adult  loses  by 
means  of  the  lungs,  skin,  and  kidneys  about  eighty  ounces  of 
water  every  twenty-four  hours.  To  restore  this  loss  about  four 
pints  must  be  taken  daily.  About  one  pint  of  this  is  obtained 
from  the  food  we  eat,  the  remaining  three  pints  being  taken  as 
drink.  One  of  the  best  ways  of  supplying  water  to  the  body 
is  by  drinking  it  in  its  pure  state,  when  its  solvent  properties 
can  be  completely  utilized.  The  amount  of  water  consumed 
depends  largely  upon  the  amount  of  work  performed  by  the 
body,  and  upon  the  temperature. 

Being  one  of  the  essential  elements  of  the  body,  it  is  highly 
important  that  water  should  be  free  from  harmful  impurities. 
If  it  contain  the  germs  of  disease,  sickness  may  follow  its  use. 
Without  doubt  the  most  important  factor  in  the  spread  of 
disease  is,  with  the  exception  of  impure  air,  impure  water. 
The  chief  agent  in  the  spread  of  typhoid  fever  is  impure  water. 
So  with  cholera,  the  evidence  is  overwhelming  that  filthy 
water  is  an  all-powerful  agent  in  the  spread  of  this  terrible 
disease. 

120.  Tea,  Coffee,  and  Cocoa.     The  active  principle  of  tea 
is  called  theine ;  that  of  coffee,  caffeine,  and  of  cocoa,  theo- 
bromine.     They  also  contain  an  aromatic,  volatile  oil,  to  which 
they  owe  their  distinctive  flavor.     Tea  and  coffee  also  contain 


FOOD    AND    DRINK.  Ill 

an  astringent  called  tannin,  which  gives  the  peculiar  bitter 
taste  to  the  infusions  when  steeped  too  long.  In  cocoa,  the 
fat  known  as  cocoa  butter  amounts  to  fifty  per  cent. 

121.  Tea.     It   has   been    estimated   that   one-half   of   the 
human  race   now  use  tea,   either   habitually  or  occasionally. 
Its  use  is  a  prolific  source  of  indigestion,  palpitation  of  the 
heart,  persistent  wakefulness,  and  of  other  disorders.     When 
used  at  all  it  should  be  only  in  moderation.     Persons   who 
cannot  use  it  without  feeling  its  hurtful  effects,  should  leave 
it  alone.     It  should  not  be  taken  on  an  empty  stomach,  nor 
sipped  after  every  mouthful  of  food. 

122.  Coffee.     Coffee  often  disturbs  the  rhythm  of  the  heart 
and  causes  palpitation.     Taken  at  night,  coffee  often  causes 
wakefulness.      This  effect  is  so  well  known   that  it  is  often 
employed  to  prevent  sleep.     Immoderate  use  of  strong  coffee 
may  produce  other  toxic  effects,  such  as  muscular  tremors, 
nervous  anxiety,  sick-headache,  palpitation,   and  various  un- 
comfortable  feelings   in   the    cardiac   region.     Some   persons 
cannot  drink  even  a  small  amount  of  tea  or  coffee  without 
these  unpleasant  effects.     These  favorite  beverages  are  unsuit- 
able for  young  people. 

123.  Cocoa.     The  beverage  known  as  cocoa  comes  from  the 
seeds  of  the  cocoa-tree,  which  are  roasted  like  the  coffee  berries 
to  develop  the  aroma.     Chocolate  is  manufactured  cocoa,— 
sugar  and  flavors  being  added  to  the  prepared  seeds.     Choco- 
late is  a  convenient  and  palatable  form  of  highly  nutritious 
food.     For  those  with  whom  tea  and  coffee  disagree,  it  may  be 
an   agreeable  beverage.     The  large  quantity  of  fat  which  it 
contains,  however,  often  causes  it  to  be  somewhat  indigestible. 

124.  Alcoholic   Beverages.     There   is   a   class   of   liquids 
which  are  certainly  not  properly  food  or  drink,  but  being  so 
commonly  used   as  beverages,  they  seem   to  require  special 


112  PRACTICAL    PHYSIOLOGY. 

notice  in  this  chapter.  In  view  of  the  great  variety  of  alcoholic 
beverages,  the  prevalence  of  their  use,  and  the  very  remarkable 
deleterious  effects  they  produce  upon  the  bodily  organism,  they 
imperatively  demand  our  most  careful  attention,  both  from  a 
physiological  and  an  hygienic  point  of  view. 

125.  Nature  of  Alcohol.  The  ceaseless  action  of  minute 
forms  of  plant  life,  in  bringing  about  the  decomposition  of  the 
elaborated  products  of  organized  plant  or  animal  structures, 
will  be  described  in  more  detail  (sees.  394-398). 

All  such  work  of  vegetable  organisms,  whether  going  on  in 
the  moulding  cheese,  in  the  souring  of  milk,  in  putrefying  meat, 
in  rotting  fruit,  or  in  decomposing  fruit  juice,  is  essentially  one 
of  fermentation,  caused  by  these  minute  forms  of  plant  life. 
There  are  many  kinds  of  fermentation,  each  with  its  own 
special  form  of  minute  plant  life  or  micro-organism. 

In  this  section  we  are  more  especially  concerned  about  that 
fermentation  which  results  from  the  decomposition  of  sweet 
fruit,  plant,  or  other  vegetable,  juices  which  are  composed 
largely  of  water  containing  sugar  and  flavoring  matters. 

This  special  form  of  fermentation  is  known  as  alcoholic  or 
vinous  fermentation,  and  the  micro-organisms  that  cause  it  are 
familiarly  termed  alcoholic  ferments.  The  botanist  classes 
them  as  Saccharomycetes,  of  which  there  are  several  varieties. 
Germs  of  Saccharomycetes  are  found  on  the  surfaces  and  stems 
of  fruit  as  it  is  ripening.  While  the  fruit  remains  whole  these 
germs  have  no  power  to  invade  the  juice,  and  even  when  the 
skins  are  broken  the  conditions  are  less  favorable  for  their 
work  than  for  that  of  the  moulds,1  which  are  the  cause  of  the 
rotting  of  fruit. 

1  The  work  of  some  kinds  of  moulds  may  be  apparent  to  the  eye,  as  in  the  growths 
that  form  on  old  leather  and  stale  bread  and  cheese.  That  of  others  goes  on  unseen, 
as  when  acids  are  formed  in  stewed  fruits.  Concerning  the  work  of  the  different 
kinds  of  moulds,  Troussart  says  :  "  Mucor  mucedo  devours  our  preserves  ;  Ascophora 
mucedo  turns  our  bread  mouldy  ;  Molinia  is  nourished  at  the  expense  of  our  fruits ; 


FOOD    AND    DRINK.  113 

But  when  fruit  is  crushed  and  its  juice  pressed  out,  the 
Saccharomycetes  are  carried  into  it  where  they  cannot  get  the 
oxygen  they  need  from  the  air.  They  are  then  able  to  obtain 
oxygen  by  taking  it  from  the  sugar  of  the  juice.  By  so  doing 
they  cause  a  breaking  up  of  the  sugar  and  a  rearrangement  of 
its  elements.  Two  new  substances  are  formed  in  this  decom- 
position of  sugar,  viz.,  carbon  dioxid,  which  arises  from  the 
liquid  in  tiny  bubbles,  and  alcohol,  a  poison  which  remains  in 
the  fermenting  fluid. 

Now  we  must  remember  that  fermentation  entirely  changes 
the  nature  of  the  substance  fermented.  For  all  forms  of 
decomposition  this  one  law  holds  good.  Before  alcoholic  fer- 
mentation, the  fruit  juice  was  wholesome  and  beneficial ;  after 
fermentation,  it  becomes,  by  the  action  of  the  minute  germs,  a 
poisonous  liquid  known  as  alcohol,  and  which  forms  an  essen- 
tial part  of  all  intoxicating  beverages. 

Taking  advantage  of  this  great  law  of  fermentation  which 
dominates  the  realm  of  nature,  man  has  devised  means  to 
manufacture  various  alcoholic  beverages  from  a  great  variety 
of  plant  structures,  as  ripe  grapes,  pears,  apples,  and  other 
fruits,  cane  juices,  corn,  the  malt  of  barley,  rye,  wheat,  and 
other  cereals. 

The  process  differs  according  to  the  substance  used  and  the 
manner  in  which  it  is  treated,  but  the  ultimate  outcome  is 
always  the  same,  viz.,  the  manufacture  of  a  beverage  contain- 
ing a  greater  or  less  proportion  of  alcoholic  poison.  By  the 
process  of  distillation,  new  and  stronger  liquor  is  made.  Bev- 
erages thus  distilled  are  known  as  ardent  spirits.  Brandy  is 
distilled  from  wine,  rum  from  fermented  molasses,  and  com- 
mercial alcohol  mostly  from  whiskey. 

Mucor  herbarium  destroys  the  herbarium  of  the  botanist ;  and  Choetonium  chartatum 
develops  itself  on  paper,  on  the  insides  of  books  and  on  their  bindings,  when  they 
come  in  contact  with  a  damp  wall."  —  TROUSSART'S  Microbes,  Ferments,  and 
Moulds. 


114  PRACTICAL    PHYSIOLOGY. 

The  poisonous  element  in  all  forms  of  intoxicating  drinks, 
and  the  one  so  fraught  with  danger  to  the  bodily  tissues,  is  the 
alcohol  they  contain.  The  proportion  of  the  alcoholic  ingre- 
dient varies,  being  about  50  per  cent  in  brandy,  whiskey,  and 
rum,  about  20  to  15  per  cent  in  wines,  down  to  5  per  cent,  or 
less,  in  the  various  beers  and  cider ;  but  whether  the  propor- 
tion of  alcohol  be  more  or  less,  the  same  element  of  danger 
is  always  present. 

.126.  Effects  of  Alcoholic  Beverages  upon  the  Human 
System.  One  of  the  most  common  alcoholic  beverages  is 
wine,  made  from  the  juice  of  grapes.  As  the  juice  flows  from 
the  crushed  fruit  the  ferments  are  washed  from  the  skins  and 
stems  into  the  vat.  Here  they  bud  and  multiply  rapidly,  pro- 
ducing alcohol.  In  a  few  hours  the  juice  that  was  sweet  and 
wholesome  while  in  the  grape  is  changed  to  a  poisonous  liquid, 
capable  of  injuring  whoever  drinks  it.  One  of  the  gravest 
dangers  of  wine-drinking  is  the  power  which  the  alcohol  in 
it  has  to  create  a  thirst  which  demands  more  alcohol.  The 
spread  of  alcoholism  in  wine-making  countries  is  an  illustration 
of  this  fact. 

Another  alcoholic  beverage,  common  in  apple-growing  dis- 
tricts, is  cider.  Until  the  microscope  revealed  the  ferment 
germ  on  the  "  bloom  "  of  the  apple-skin,  very  little  was  known 
of  the  changes  produced  in  cider  during  the  mysterious  process 
of  "working."  Now,  when  we  see  the  bubbles  of  gas  in  the 
glass  of  cider  we  know  what  has  produced  them,  and  we  know 
too  that  a  poison  which  we  do  not  see  is  there  also  in  corre- 
sponding amounts.  We  have  learned,  too,  to  trace  the  wrecked 
hopes  of  many  a  farmer's  family  to  the  alcohol  in  the  cider 
which  he  provided  so  freely,  supposing  it  harmless. 

Beer  and  other  malt  liquors  are  made  from  grain.  By 
sprouting  the  grain,  which  changes  its  starch  to  sugar,  and 
then  dissolving  out  the  sugar  with  water,  a  sweet  liquid  is 


FOOD    AND    DRINK.  115 

obtained  which  is  fermented  with  yeast,  one  kind  of  alcoholic 
ferment.  Some  kinds  of  beer  contain  only  a  small  percentage 
of  alcohol,  but  these  are  usually  drunk  in  proportionately  large 
amounts.  The  life  insurance  company  finds  the  beer  drinker 
a  precarious  risk ;  the  surgeon  finds  him  an  unpromising  sub- 
ject ;  the  criminal  court  finds  him  conspicuous  in  its  proceed- 
ings. The  united  testimony  from  all  these  sources  is  that  beer 
is  demoralizing,  mentally,  morally,  and  physically. 

127.  Cooking.  The  process  through  which  nearly  all  food 
used  by  civilized  man  has  to  pass  before  it  is  eaten  is  known  as 
cooking.  Very  few  articles  indeed  are  consumed  in  their  natural 
state,  the  exceptions  being  eggs,  milk,  oysters,  fruit  and  a  few  vege- 
tables. Man  is  the  only  animal  that  cooks  his  food.  Although 
there  are  savage  races  that  have  no  knowledge  of  cooking, 
civilized  man  invariably  cooks  most  of  his  food.  It  seems  to 
be  true  that  as  nations  advance  in  civilization  they  make  a 
proportionate  advance  in  the  art  of  cooking. 

Cooking  answers  most  important  purposes  in  connection 
with  our  food,  especially  from  its  influence  upon  health.  It 
enables  food  to  be  more  readily  chewed,  and  more  easily 
digested.  Thus,  a  piece  of  meat  when  raw  is  tough  and  tena- 
cious, but  if  cooked  the  fibers  lose  much  of  their  toughness, 
while  the  connective  tissues  are  changed  into  a  soft  and  jelly- 
like  mass.  Besides,  the  meat  is  much  more  readily  masticated 
and  acted  upon  by  the  digestive  fluids.  So  cooking  makes 
vegetables  and  grains  softer,  loosens  their  structure,  and  en- 
ables the  digestive  juices  readily  to  penetrate  their  substance. 

Cooking  also  improves  or  develops  flavors  in  food,  especially 
in  animal  foods,  and  thus  makes  them  attractive  and  pleasant 
to  the  palate.  The  appearance  of  uncooked  meat,  for  example, 
is  repulsive  to  our  taste,  but  by  the  process  of  cooking,  agree- 
able flavors  are  developed  which  stimulate  the  appetite  and 
the  flow  of  digestive  fluids. 


Il6  PRACTICAL    PHYSIOLOGY. 

Another  important  use  of  cooking  is  that  it  kills  any  minute 
parasites  or  germs  in  the  raw  food.  The  safeguard  of  cooking 
thus  effectually  removes  some  important  causes  of  disease. 
The  warmth  that  cooking  imparts  to  food  is  a  matter  of  no 
slight  importance ;  for  warm  food  is  more  readily  digested,  and 
therefore  nourishes  the  body  more  quickly. 

The  art  of  cooking  plays  a  very  important  part  in  the  matter 
of  health,  and  thus  of  comfort  and  happiness.  Badly  cooked 
and  ill-assorted  foods  are  often  the  cause  of  serious  disorders. 
Mere  cooking  is  not  enough,  but  good  cooking  is  essential. 

EXPERIMENTS. 
EXPERIMENTS  WITH  THE  PROTEIDS. 

31.  As  a  type  of  the  group  of  proteids  we  take  the  white  of  egg,  egg- 
white  or  egg-albumen.     Break  an  egg  carefully,  so  as  not  to  mix  the  white 
with  the  yolk.    Drop  about  half  a  teaspoonful  of  the  raw  white  of  egg  into 
half  a  pint  of  distilled  water.     Beat  the  mixture  vigorously  with  a  glass 
rod  until  it  froths  freely.     Filter  through  several  folds  of  muslin  until  a 
fairly  clear  solution  is  obtained. 

32.  •  To  a  small  quantity  of  this  solution  in  a  test  tube  add  strong  nitric 
acid,  and  boil.    Note  the  formation  of  a  white  precipitate,  which  turns  yellow. 
After  cooling,  add  ammonia,  and  note  that  the  precipitate  becomes  orange. 

33.  Add  to  the  solution  of  egg-albumen,  excess  of  strong  solution  of 
caustic  soda  (or  potash),  and  then  a  drop  or  two  of  very  dilute  solution  (one 
per  cent)  of  copper  sulphate.    A  violet  color  is  obtained  which  deepens  on 
boiling. 

34.  Boil  a  small  portion  of  the  albumen  solution  in  a  test  tube,  adding 
drop  by  drop  dilute  acetic  acid  (two  per  cent)  until  a  flaky  coagulum  of 
insoluble  albumen  separates. 

EXPERIMENTS  WITH  STARCH. 

35.  Wash  a  potato  and  peel  it.     Grate  it  on  a  nutmeg  grater  into  a 
tall  cylindrical  glass  full  of  water.     Allow  the  suspended  particles  to  sub- 
side, and  after  a  time  note  the  deposit.     The  lowest  layer  consists  of  a 
white  powder,  or  starch,  and  above  it  lie  coarser  fragments  of  cellulose  and 
other  matters. 


FOOD    AND    DRINK.  1 1/ 

36.  Examine  under  the  microscope  a  bit  of  the  above  white  deposit. 
Note  that  each  starch  granule  shows  an  eccentric  hilum  with  concentric 
markings.   Add  a  few  drops  of  very  dilute  solution  of  iodine.    Each  granule 
becomes  blue,  while  the  markings  become  more  distinct. 

37.  Examine  a  few  of  the  many  varieties  of  other  kinds  of  starch 
granules,   as   in   rice,  arrowroot,   etc.       Press    some    dry   starch   powder 
between  the  thumb  and  forefinger,  and  note  the  peculiar  crepitation. 

38.  Rub  a  few  bits  of  starch  in  a  little  cold  water.     Put  a  little  of  the 
mixture  in  a  large  test  tube,  and  then  fill  with  boiling  water.     Boil  until  an 
imperfect  opalescent  solution  is  obtained. 

39.  Add  powdered  dry  starch  to  cold  water.    It  is  insoluble.    Filter  and 
test  the  filtrate  with  iodine.     It  gives  no  blue  color. 

40.  Boil  a  little  starch  with  water ;  if  there  is  enough  starch  it  sets  on 
cooling  and  a  paste  results. 

41.  Moisten  some  flour  with  water  until  it  forms  a  tough,  tenacious 
dough ;  tie  it  in  a  piece  of  cotton  cloth,  and  knead  it  in  a  vessel  containing 
water  until  all  the  starch  is  separated.     There  remains  on  the  cloth  a 
grayish  white,  sticky,  elastic  "gluten,"  made  up  of  albumen,  some  of  the 
ash,  and  fats.     Draw  out  some  of  the  gluten  into  threads,  and  observe  its 
tenacious  character. 

42.  Shake  up  a  little  flour  with  ether  in  a  test  tube,  with  a  tight-fitting 
cork.    Allow  the  mixture  to  stand  for  an  hour,  shaking  it  from  time  to  time. 
Filter  off  the  ether,  and  place  some  of  it  on  a  perfectly  clean  watch  glass. 
Allow  the  ether  to  evaporate,  when  a  greasy  stain  will  be  left,  thus  showing 
the  presence  of  fats  in  the  flour. 

43.  Secure  a  specimen  of  the  various  kinds  of  flour,  and  meal,  peas, 
beans,  rice,  tapioca,  potato,  etc.     Boil  a  small  quantity  of  each  in  a  test 
tube  for  some  minutes.     Put  a  bit  of  each  thus  cooked  on  a  white  plate, 
and  pour  on  it  two  or  three  drops  of  the  tincture  of  iodine.     Note  the 
various  changes  of  color,  —  blue,  greenish,  orange,  or  yellowish. 

EXPERIMENTS  WITH  MILK. 

44.  Use  fresh  cow's  milk.    Examine  the  naked-eye  character  of  the  milk. 
Test  its  reaction  with  litmus  paper.     It  is  usually  neutral  or  slightly  alkaline. 

45.  Examine  with  the  microscope  a  drop   of  milk,  noting  numerous 
small,  highly  refractive  oil  globules  floating  in  a  fluid. 

46.  Dilute  one  ounce  of  milk  with  ten  times  its  volume  of  water.     Add 
cautiously  dilute  acetic  acid  until  there  is  a  copious,  granular-looking  pre- 


Il8  PRACTICAL  PHYSIOLOGY. 

cipitate  of  the  chief  proteid  of  milk  (caseinogen),  formerly  regarded  as  a 
derived  albumen.     This  action  is  hastened  by  heating. 

47.  Saturate  milk  with  Epsom  salts,  or  common  salt.     The  proteid  and 
fat  separate,  rise  to  the  surface,  and  leave  a  clear  fluid  beneath. 

48.  Place  some  milk  in  a  basin  ;  heat  it  to  about  100°  F.,  and  add  a  few 
drops  of  acetic  acid.     The  mass  curdles  and  separates  into  a  solid  curd 
(proteid  and  fat)  and  a  clear  fluid  (the  whey),  which  contains  the  lactose. 

49.  Take  one  or  two  teaspoonf uls  of  fresh  milk  in  a  test  tube  ;  heat  it, 
and  add  a  small  quantity  of  extract  of  rennet.     Note  that  the  whole  mass 
curdles  in  a  few  minutes,  so  that  the  tube  can  be  inverted  without  the  curd 
falling  out.      Soon  the  curd  shrinks,   and  squeezes    out  a  clear,  slightly 
yellowish  fluid,  the  whey. 

50.  Boil  the  milk  as  before,  and  allow  it  to  cool ;  then  add  rennet.    No 
coagulation  will  probably  take  place.    It  is  more  difficult  to  coagulate  boiled 
milk  with  rennet  than  unboiled  milk. 

51.  Test  fresh  milk  with  red  litmus  paper;  it  should  turn  the  paper  pale 
blue,  showing  that  it  is  slightly  alkaline.     Place  aside  for  a  day  or  two,  and 
then  test  with  blue  litmus  paper  ;  it  will  be  found  to  be  acid.     This  is  due 
to  the  fact  that  lactose  undergoes  the  lactic  acid  fermentation.    The  lactose 
is  converted  into  lactic  acid  by  means  of  a  special  ferment. 

52.  Evaporate  a  small  quantity  of  milk  to  dryness  in  an  open  dish. 
After  the  dry  residue  is  obtained,  continue  to  apply  heat ;  observe  that  it 
chars  and  gives  off  pungent  gases.     Raise  the  temperature  until  it  is  red 
hot ;  allow  the  dish  then  to  cool ;  a  fine  white  ash  will  be  left  behind.    This 
represents  the  inorganic  matter  of  the  milk. 

EXPERIMENTS  WITH  THE  SUGARS. 

53.  Cane  sugar  is  familiar  as  cooking  and  table  sugar.    The  little  white 
grains  found  with  raisins  are  grape  sugar,  or  glucose.    Milk  sugar  is  readily 
obtained  of  the  druggist.     Prepare  a  solution  of  the  various  sugars  by 
dissolving  a  small  quantity  of  each  in  water.     Heat  each  solution  with  sul- 
phuric acid,  and  it  is  seen  to  darken  or  char  slowly. 

54.  Place  some  Fehling  solution  (which  can  be  readily  obtained  at  the 
drug  store  as  a  solution,  or  tablets  may  be  bought  which  answer  the  same 
purpose)  in  a  test  tube,  and  boil.    If  no  yellow  discoloration  takes  place,  it 
is  in  good  condition.     Add  a  few  drops  of  the  grape  sugar  solution  and 
boil,  when  the  mixture  suddenly  turns  to  an  opaque  yellow  or  red  color. 

55.  Repeat  same  experiment  with  milk  sugar. 


CHAPTER   VI. 
DIGESTION. 

128.  The  Purpose  of  Digestion.     As  we  have  learned,  our 
bodies  are  subject  to  continual  waste,  due  both  to  the  wear  and 
tear  of  their  substance,  and  to  the  consumption  of  material  for 
the  production  of  their  heat  and  energy.      The  waste  occurs  in 
no  one  part  alone,  but  in  all  the  tissues. 

Now,  the  blood  comes  into  direct  contact  with  every  one  of 
these  tissues.  The  ultimate  cells  which  form  the  tissues  are 
constantly  being  bathed  by  the  myriads  of  minute  blood-vessels 
which  bring  to  the  cells  the  raw  material  needed  for  their 
continued  renewal.  These  cells  are  able  to  select  from  the 
nutritive  fluid  whatever  they  require  to  repair  their  waste,  and 
to  provide  for  their  renewed  activity.  At  the  same  time,  the 
blood,  as  it  bathes  the  tissues,  sweeps  into  its  current  and 
bears  away  the  products  of  waste. 

Thus  the  waste  occurs  in  the  tissues  and  the  means  of  repair 
are  obtained  from  the  blood.  The  blood  is  thus  continually 
being  impoverished  by  having  its  nourishment  drained  away. 
How,  then,  is  the  efficiency  of  the  blood  maintained?  The 
answer  is  that  while  the  ultimate  purpose  of  the  food  is  for 
the  repair  of  the  waste,  its  immediate  destination  is  the  blood.1 

129.  Absorption  of   Food  by  the  Blood.      How  does  the 
food  pass  from  the  cavity  of  the  stomach  and  intestinal  canal 
into  the  blood-vessels?     There  are  no  visible  openings  which 

1 "  The  physiological  wear  of  the  organism  is  constantly  being  repaired  by  the 
blood ;  but  in  order  to  keep  the  great  nutritive  fluid  from  becoming  impoverished, 
the  matters  which  it  is  constantly  losing  must  be  supplied  from  some  source  out  of 
the  body,  and  this  necessitates  the  ingestion  of  articles  which  are  known  as  food."  — 
FLINT'S  Text-book  of  Human  Physiology. 


120 


PRACTICAL  PHYSIOLOGY. 


permit  communication.  It  is  done  by  what  in  physics  is  known 
as  endosmotic  and  exosmotic  action.  That  is,  whenever  there 
are  two  solutions  of  different  densities,  separated  only  by  an 
animal  membrane,  an  interchange  will  take  place  between  them 
through  the  membrane. 

To   illustrate :    in  the  walls  of  the  stomach  and   intestines 
there  is  a  network  of  minute  vessels  filled  with  blood,  —  a  liquid 

containing  many 
substances  in  solu- 
tion. The  stomach 
and  intestinal  canal 
also  contain  liquid 
food,  holding  many 
substances  in  solu- 
tion. A  membrane, 
made  up  of  the  ex- 
tremely thin  walls  of 
the  blood-vessels 
and  intestines,  sep- 
arates the  liquids. 
An  exchange  takes 
place  between  the 
blood  and  the  con- 
tents of  the  stomach 

FIG.  46.  —  Cavities  of  the  Mouth,  Pharynx,  etc.  (Section 

in  the  middle  line  designed  to  show  the  mouth  in  its  and  OOWe\S,  by  which 

relations  to  the  nasal  fossae,  the  pharynx,  and  the  the     dissolved     Sub- 

larynx.)  stances  of  food  pass 

A,  sphenoidal  sinus ;   B,  internal  orifice  of  Eustachian  tube  ;    through  the  SCparat- 
C,  velum  palati ;   D,  anterior  pillar  of  soft  palate;   E,  pos- 
terior pillar  of  soft  palate ;  F,  tonsil;  H,  lingual  portion  of   mg  membranes  into 

the  pharynx;   K,  lower  portion  of  the  pharynx;   L,  larynx;    $16  blood 
M,  section  of  hyoid  bone  ;  N,  epiglottis  ;  O,  palatine  arch. 

This    change,    by 

which  food  is  made  ready  to  pass  into  the  blood,  constitutes 
food-digestion,  and  the  organs  concerned  in  bringing  about 
this  change  in  the  food  are  the  digestive  organs. 


DIGESTION.  121 

130.  The  General  Plan  of  Digestion.  It  is  evident  that 
the  digestive  organs  will  be  simple  or  complex,  according  to 
the  amount  of  change  which  is  necessary  to  prepare  the  food 
to  be  taken  up  by  the  blood.  If  the  requisite  change  is  slight, 
the  digestive  organs  will  be  few,  and  their  structure  simple. 
But  if  the  food  is  varied  and  complex  in  composition,  the 


FIG.  47. —  Diagram  of  the  Structure  of  Secreting  Glands. 

A,  simple  tubular  gland ;   B,  gland  with  mouth  shut  and  sac  formed  ;   C,  gland  with  a 
coiled  tube  ;   D,  plan  of  part  of  a  racemose  gland. 

digestive  apparatus  will  be  complex.     This  condition  applies 
to  the  food  and  the  digestion  of  man. 

The  digestive  apparatus  of  the  human  body  consists  of  the 
alimentary  canal  and  tributary  organs  which,  although  outside 
of  this  canal,  communicate  with  it  by  ducts.  The  alimentary 
canal  consists  of  the  mouth,  the  pharynx,  the  oesophagus,  the 
stomach,  and  the  intestines.  Other  digestive  organs  which 
are  tributary  to  this  canal,  and  discharge  their  secretions  into 
it,  are  the  salivary  glands,1  the  liver,  and  the  pancreas. 

1  Glands.  Glands  are  organs  of  various  shapes  and  sizes,  whose  special  work  it  is 
to  separate  materials  from  the  blood  for  further  use  in  the  body,  the  products  being 
known  as  secretion  and  excretion.  The  means  by  which  secretion  and  excretion 
are  effected  are,  however,  identical.  The  essential  parts  of  a  gland  consist  of  a  base- 
ment membrane,  on  one  side  of  which  are  found  actively  growing  cells,  on  the  other 
is  the  blood  current,  flowing  in  exceedingly  thin-walled  vessels  known  as  the  capil- 
laries. The  cells  are  able  to  select  from  the  blood  whatever  material  they  require 
and  which  they  elaborate  into  the  particular  secretion.  In  Fig.  47  is  illustrated, 
diagrammatically,  the  structure  of  a  few  typical  secreting  glands.  The  continuous 
line  represents  the  basement  membrane.  The  dotted  line  represents  the  position  of 
the  cells  on  one  side  of  the  basement  membrane.  The  irregular  lines  show  the  posi- 
tion of  the  blood-vessels. 


122  PRACTICAL  PHYSIOLOGY. 

The  digestive  process  is  subdivided  into  three  steps,  which 
take  place  in  the  mouth,  in  the  stomach,  and  in  the  intestines. 

131.  The  Mouth.     The  mouth  is  the  cavity  formed  by  the 
lips,  the  cheeks,  the  palate,  and  the  tongue.     Its  bony  roof 
is  made  up  of  the  upper  jawbone  on  each  side,  and  the  palate 
bones  behind.     This  is  the  hard  palate,   and  forms  only  the 
front  portion  of  the  roof.    The  continuation  of  the  roof  is  called 
the  soft  palate,  and  is  made  up  of  muscular  tissue  covered  with 
mucous  membrane. 

The  mouth  continues  behind  into  the  throat,  the  separation 
between  the  two  being  marked  by  fleshy  pillars  which  arch  up 
from  the  sides  to  form  the  soft  palate.  In  the  middle  of  this 
arch  there  hangs  from  its  free  edge  a  little  lobe  called  the 
uvula.  On  each  side  where  the  pillars  begin  to  arch  is  an 
almond-shaped  body  known  as  the  tonsil.  When  we  take  cold, 
one  or  both  of  the  tonsils  may  become  inflamed,  and  so  swollen 
as  to  obstruct  the  passage  into  the  throat.  The  mouth  is  lined 
with  mucous  membrane,  which  is  continuous  with  that  of  the 
throat,  oesophagus,  stomach,  and  intestines  (Fig.  51). 

132.  Mastication,  or  Chewing.     The  first  step  of  the  pro- 
cess of  digestion  is  mastication,  the  cutting  and  grinding  of 
the  food  by  the  teeth,  effected  by  the  vertical  and  lateral  move- 
ments of  the  lower  jaw.     While  the  food  is  thus  being  crushed, 
it  is  moved  to  and  fro  by  the  varied  movements  of  the  tongue, 
that  every  part  of  it  may  be  acted  upon  by  the  teeth.     The 
advantage  of  this  is  obvious.    The  more  finely  the  food  is  divided, 
the  more  easily  will  the  digestive  fluids  reach  every  part  of  it, 
and  the  more  thoroughly  and  speedily  will  digestion  ensue. 

The  act  of  chewing  is  simple  and  yet  important,  for  if  hur- 
riedly or  imperfectly  done,  the  food  is  in  a  condition  to  cause 
disturbance  in  the  digestive  process.  Thorough  mastication 
is  a  necessary  introduction  to  the  more  complicated  changes 
which  occur  in  the  later  digestion. 


DIGESTION.  '  123 

133.  The  Teeth.  The  teeth  are  attached  to  the  upper  and 
lower  maxillary  bones  by  roots  which  sink  into  the  sockets  of 
the  jaws.  Each  tooth  consists  of  a  crown,  the  visible  part, 
and  one  or  more  fangs,  buried  in  the  sockets.  There  are  in 
adults  32  teeth,  16  in  each  jaw. 

Teeth  differ  in  name  according  to  their  form  and  the  uses 
to  which  they  are  specially  adapted.  Thus,  at  the  front  of  the 
jaws,  the  incisors,  or  cutting  teeth,  number  eight,  two  on  each 
side.  They  have  a  single  root  and  the  crown  is  beveled  behind, 
presenting  a  chisel-like  edge.  The  incisors  divide  the  food,  and 
are  well  developed  in  rodents,  as  squirrels,  rats,  and  beavers. 

Next  come  the  canine  teeth,  or  cuspids,  two  in  each  jaw,  so 
called  from  their  resemblance  to  the  teeth  of  dogs  and  other 
flesh-eating  animals.  These  teeth  have  single  roots,  but  their 
crowns  are  more  pointed  than  in  the  incisors.  The  upper  two 
are  often  called  eye  teeth,  and  the  lower  two,  stomach  teeth. 
Next  behind  the  canines  follow,  on  each  side,  two  bicuspids. 
Their  crowns  are  broad,  and  they  have  two  roots.  The  three 
hindmost  teeth  in  each  jaw  are  the  molars,  or  grinders.  These 
are  broad  teeth  with  four  or  five  points  on  each,  and  usually 
each  molar  has  three  roots. 

The  last  molars  are  known  as  the  wisdom  teeth,  as  they  do 
not  usually  appear  until  the  person  has  reached  the  "  years 
of  discretion."  All  animals  that  live  on  grass,  hay,  corn,  and 
the  cereals  generally,  have  large  grinding  teeth,  as  the  horse, 
ox,  sheep,  and  elephant. 

The  following  table  shows  the  teeth  in  their  order  : 

Mo.  Bi.  Ca.   In.  In.  Ca.  Bi.  Mo. 


Upper  3212 
Lower  3212 


i      2       3   =  16 


I         2 


The  vertical  line  indicates  the  middle  of  the  jaw,  and  shows 
that  on  each  side  of  each  jaw  there  are  eight  teeth. 


124  PRACTICAL  PHYSIOLOGY. 

134.  Development  of  the  Teeth.  The  teeth  just  described  are  the 
permanent  set,  which  succeeds  the  temporary  or  milk  teeth.  The 
latter  are  twenty  in  number,  ten  in  each  jaw,  of  which  the  four  in 
the  middle  are  incisors.  The  tooth  beyond  on  each  side  is  an  eye 
tooth,  and  the  next  two  on  each  side  are  bicuspids,  or  premolars. 

The  milk  teeth  appear  during  the  first  and  second  years,  and  last 
until  about  the  sixth  or  seventh  year,  from  which  time  until  the  twelfth 


FIG.  48.  —  Temporary  and  Permanent  Teeth  together. 

Temporary  teeth:  A,  central  incisors;  B,  lateral  incisors;  C,  canines;  D,  anterior 
molars;  E,  posterior  molars.  Permanent  teeth:  F,  central  incisors;  H,  lateral 
incisors;  K,  canines;  L,  first  bicuspids;  M,  second  biscuspids ;  N,  first  molars. 

or  thirteenth  year,  they  are  gradually  pushed  out,  one  by  one,  by  the 
permanent  teeth.  The  roots  of  the  milk  teeth  are  much  smaller  than 
those  of  the  second  set. 

The  plan  of  a  gradual  succession  of  teeth  is  a  beautiful  provision 
of  nature,  permitting  the  jaws  to  increase  in  size,  and  preserving  the 
relative  position  and  regularity  of  the  successive  teeth. 

135.  Structure  of  the  Teeth.  If  we  should  saw  a  tooth  down 
through  its  center  we  would  find  in  the  interior  a  cavity.  This 
is  the  pulp  cavity,  which  is  filled  with  the  dental  pulp,  a  deli- 


DIGESTION. 


125 


FIG.  49.  —  Showing  the  Principal  Organs  of  the  Thorax  and  Abdomen  in  situ.    (The 
•    principal  muscles  are  seen  on  the  left,  and  superficial  veins  on  the  right.) 


126 


PRACTICAL    PHYSIOLOGY. 


cate  substance  richly  supplied  with  nerves  and  blood-vessels, 
which  enter  the  tooth  by  small  openings  at  the  point  of  the  root. 
The  teeth  are  thus  nourished  like  other  parts  of  the  body.  The 
exposure  of  the  delicate  pulp  to  the  air,  due  to  the  decay  of 
the  dentine,  gives  rise  to  the  pain  of  toothache. 

Surrounding  the  cavity  on  all  sides  is  the  hard  substance 
known  as  the  dentine,  or  tooth  ivory.  Outside  the  dentine  of 
the  root  is  a  substance  closely  resembling  bone,  called  cement. 
In  fact,  it  is  true  bone,  but  lacks  the  Haversian  canals.  The 
root  is  held  in  its  socket  by  a  dense 
fibrous  membrane  which  surrounds  the 
cement  as  the  periosteum  does  bone. 
The  crown  of  the  tooth  is  not  covered 
by  cement,  but  by  the  hard  enamel, 
which  forms  a  strong  protection  for 
the  exposed  part.  When  the  teeth  are 
first  "  cut,"  the  surface  of  the  enamel  is 
coated  with  a  delicate  membrane  which 
answers  to  the  Scriptural  phrase  "  the 
skin  of  the  teeth."  This  is  worn  off 

in  adult  life. 
FIG.   50.  —  Section   of    Face. 
(Showing  the  parotid  and 
submaxillary  glands.)  13*>'    InSallVatlOn.       The    thorough 

mixture  of  the  saliva  with  the  food  is 

called  insalivation.  While  the  food  is  being  chewed,  it  is 
moistened  with  a  fluid  called  saliva,  which  flows  into  the 
mouth  from  six  little  glands.  There  are  on  each  side  of  the 
mouth  three  salivary  glands,  which  secrete  the  saliva  from 
the  blood.  The  parotid  is  situated  on  the  side  of  the  face  in 
front  of  the  ear.  The  disease,  common  in  childhood,  during 
which  this  gland  becomes  inflamed  and  swollen,  is  known  as  the 
"  mumps."  The  submaxillary  gland  is  placed  below  and  to 
the  inner  side  of  the  lower  jaw,  and  the  sublingual  is  on  the 
floor  of  the  mouth,  between  the  tongue  and  the  gums.  Each 


DIGESTION.  127 

gland  opens  into  the  mouth  by  a  little  duct.  These  glands 
somewhat  resemble  a  bunch  of  grapes  with  a  tube  for  a  stalk. 

The  saliva  is  a  colorless  liquid  without  taste  or  smell.  Its 
principal  element,  besides  water,  is  a  ferment  called  ptyalin, 
which  has  the  remarkable  property  of  being  able  to  change 
starch  into  a  form  of  cane-sugar,  known  as  maltose. 

Thus,  while  the  food  is  being  chewed,  another  process  is 
going  on  by  which  starch  is  changed  into  sugar.  The  saliva 
also  moistens  the  food  into  a  mass  for  swallowing,  and  aids  in 
speech  by  keeping  the  mouth  moist. 

The  activity  of  the  salivary  glands  is  largely  regulated  by 
their  abundant  supply  of  nerves.  Thus,  the  saliva  flows  into 
the  mouth,  even  at  the  sight,  smell,  or  thought  of  food.  This 
is  popularly  known  as  "making  the  mouth  water."  The  flow 
of  saliva  may  be  checked  by  nervous  influences,  as  sudden 
terror  and  undue  anxiety. 

Experiment  56.  To  show  the  action  of  saliva  on  starch.  Saliva  for 
experiment  may  be  obtained  by  chewing  a  piece  of  India  rubber  and  collect- 
ing the  saliva  in  a  test  tube.  Observe  that  it  is  colorless  and  either  trans- 
parent or  translucent,  and  when  poured  from  one  vessel  to  another  is 
glairy  and  more  or  less  adhesive.  Its  reaction  is  alkaline  to  litmus  paper. 

Experiment  57.  Make  a  thin  paste  from  pure  starch  or  arrowroot. 
Dilute  a  little  of  the  saliva  with  five  volumes  of  water,  and  filter  it.  This 
is  best  done  through  a  filter  perforated  at  its  apex  by  a  pin-hole.  In  this 
way  all  air-bubbles  are  avoided.  Label  three  test  tubes  A,  B,  and  C. 
In  A,  place  starch  paste;  in  B,  saliva;  and  in  C  one  volume  of  saliva  and 
three  volumes  of  starch  paste.  Place  them  for  ten  minutes  in  a  water  bath 
at  about  104°  Fahrenheit. 

Test  portions  of  all  three  for  a  reducing  sugar,  by  means  of  Fehling's 
solution  or  tablets.1  A  and  B  give  no  evidence  of  sugar,  while  C  reduces 
the  Fehling,  giving  a  yellow  or  red  deposit  of  cuprous  oxide.  Therefore, 
starch  is  converted  into  a  reducing  sugar  by  the  saliva.  This  is  done  by 
the  ferment  ptyalin  contained  in  saliva. 

1  Tablets  and  other  material  for  Fehling  and  additional  tests  for  sugar  can  be  pur- 
chased at  a  drug  store.  The  practical  details  of  these  and  other  tests  which  assume 
some  knowledge  of  chemistry,  should  be  learned  from  some  manual  on  the  subject. 


128  PRACTICAL    PHYSIOLOGY. 

137.  The  Pharynx  and   (Esophagus.     The  dilated  upper 
part  of  the  alimentary  canal  is  called  the  pharynx.     It  forms  a 
blind  sac  above  the  level  of  the  mouth.     The  mouth  opens 
directly  into  the  pharynx,  and  just  above  it  are  two  openings 
leading  into  the  posterior  passages  of  the  nose.     There  are  also 
little  openings,  one  on  each  side,  from  which  begin  the  Eusta- 
chian  tubes,  which  lead  upward  to  the  ear  cavities. 

The  windpipe  opens  downward  from  the  pharynx,  but  this 
communication  can  be  shut  off  by  a  little  plate  or  lid  of  cartilage, 
the  epiglottis.  During  the  act  of  swallowing,  this  closes  down 
over  the  entrance  to  the  windpipe,  like  a  lid,  and  prevents  the 
food  from  passing  into  the  air-passages.  This  tiny  trap-door 
can  be  seen,  by  the  aid  of  a  mirror,  if  we  open  the  mouth  wide 
and  press  down  the  back  of  the  tongue  with  the  handle  of  a 
spoon  (Figs.  46,  84,  and  85). 

Thus,  there  are  six  openings  from  the  pharynx  ;  the  oesopha- 
gus being  the  direct  continuation  from  it  to  the  stomach.  If  we 
open  the  mouth  before  a  mirror  we  see  through  the  fauces  the 
rear  wall  of  the  pharynx.  In  its  lining  membrane  is  a  large 
number  of  glands,  the  secretion  from  which  during  a  severe 
cold  may  be  quite  troublesome. 

The  oesophagus,  or  gullet,  is  a  tube  about  nine  inches  long, 
reaching  from  the  throat  to  the  stomach.  It  lies  behind  the 
windpipe,  pierces  the  diaphragm  between  the  chest  and  abdo- 
men, and  opens  into  the  stomach.  It  has  in  its  walls  muscular 
fibers,  which,  by  their  worm-like  contractions,  grasp  the  suc- 
cessive masses  of  food  swallowed,  and  pass  them  along  down- 
wards into  the  stomach. 

138.  Deglutition,  or  Swallowing.     The  food,  having  been 
well  chewed  and  mixed  with  saliva,  is  now  ready  to  be  swal- 
lowed as  a  soft,  pasty  mass.     The  tongue  gathers  it  up  and 
forces  it  backwards  between  the  pillars  of  the  fauces  into  the 
pharynx. 


DIGESTION. 


I29 


If  we  place  the  fingers  on  the  "  Adam's  apple,  "  and  then 
pretend  to  swallow  something,  we  can  feel  the  upper  part  of  the 
windpipe  and  the  closing  of  its  lid  (epiglottis),  so  as  to  cover 
the  entrance  and  prevent  the 
passage  of  food  into  the 
trachea. 

There  is  only  one  pathway 
for  the  food  to  travel,  and 
that  is  down  the  oesophagus. 
The  slow  descent  of  the  food 
may  be  seen  if  a  horse  or  dog 
be  watched  while  swallowing. 
Even  liquids  do  not  fall  or 
flow  down  the  food  passage. 
Hence,  acrobats  can  drink 
while  standing  on  their  heads, 
or  a  horse  with  its  mouth 
below  the  level  of  the  oeso- 
phagus. The  food  is  under 
the  control  of  the  will  until  it 
has  entered  the  pharynx  ;  all 
the  later  movements  are  in- 
voluntary. 


FIG.  51.  — A  View  into  the  Back  Part  of 
the  Adult  Mouth.  (The  head  is  repre- 
sented as  having  been  thrown  back,  and 
the  tongue  drawn  forward.) 

A,  B,  incisors;  C,  canine;  D,  E,  bicuspids; 
F,  H,  K,  molars ;  M,  anterior  pillar  of  the 
fauces;  N,  tonsil;  L,  uvula;  O,  upper 
part  of  the  pha:/nx;  P,  tongue  drawn 
forward  ;  R,  linear  ridge,  or  raph£. 

easily  described.     It  has  been 

compared  to  a  bagpipe,  which  it  resembles  somewhat,  when 
moderately  distended.  When  empty  it  is  flattened,  and  in 
some  parts  its  opposite  walls  are  in  contact. 

We  may  describe  the  stomach  as  a  pear-shaped  bag,  with  the 


139.  The  Stomach.  The 
stomach  is  the  most  dilated 
portion  of  the  alimentary 
canal  and  the  principal  organ 
of  digestion.  Its  form  is  not 


I3O  PRACTICAL  PHYSIOLOGY. 

large  end  to  the  left  and  the  small  end  to  the  right.  It  lies 
chiefly  on  the  left  side  of  the  abdomen,  under  the  diaphragm, 
and  protected  by  the  lower  ribs.  The  fact  that  the  large  end 
of  the  stomach  lies  just  beneath  the  diaphragm  and  the  heart, 
and  is  sometimes  greatly  distended  on  account  of  indigestion 
or  gas,  may  cause  feelings  of  heaviness  in  the  chest  or  palpita- 


D 

FIG.  52.  — The  Stomach. 
A,  cardiac  end ;   B,  pyloric  end ;  C,  lesser  curvature ;  D,  greater  curvature. 

tion  of  the  heart.  The  stomach  is  subject  to  greater  variations 
in  size  than  any  other  organ  of  the  body,  depending  on  its  con- 
tents. Just  after  a  moderate  meal  it  averages  about  twelve 
inches  in  length  and  four  in  diameter,  with  a  capacity  of  about 
four  pints. 

The  orifice  by  which  the  food  enters  is  called  the  cardiac 
opening,  because  it  is  near  the  heart.  The  other  opening,  by 
which  the  food  leaves  the  stomach,  and  where  the  small  intes- 
tine begins,  is  the  pyloric  orifice,  and  is  guarded  by  a  kind  of 
valve,  known  as  the  pylorus,  or  gatekeeper.  The  concave 
border  between  the  two  orifices  is  called  the  small  curvature, 
and  the  convex  as  the  great  curvature,  of  the  stomach. 


DIGESTION. 


140.  Coats  of  Stomach.  The  walls  of  the  stomach  are  formed  by 
four  coats,  known  successively  from  without  as  serous,  muscular, 
sub-mucous,  and  mucous.  The  outer  coat  is  the  serous  membrane 
which  lines  the  abdomen, —  the  peritoneum  (note,  p.  135).  The  second 
coat  is  muscular,  having  three  sets  of  involuntary  muscular  fibers. 
The  outer  set  runs  lengthwise  from  the  cardiac  orifice  to  the  pylorus. 
The  middle  set  encircles  all  parts  of  the  stomach,  while  the  inner  set 
consists  of  oblique  fibers.  The  third 
coat  is  the  sub-mucous,  made  up  of 
loose  connective  tissues,  and  binds  the 
mucous  to  the  muscular  coat.  Lastly 
there  is  the  mucous  coat,  a  moist,  pink, 
inelastic  membrane,  which  completely 
lines  the  stomach.  When  the  stomach 
is  not  distended,  the  mucous  layer  is 
thrown  into  folds  presenting  a  corru- 
gated appearance. 


FIG.  53.— Pits  in  the  Mucous 
Membrane  of  the  Stomach,  and 
Openings  of  the  Gastric  Glands. 
(Magnified  20  diameters.) 


141.  The  Gastric  Glands.    If  we 

were  to  examine  with  a  hand  lens 
the  inner  surface  of  the  stomach, 
we  would  find  it  covered  with  little 
pits,  or  depressions,  at  the  bottom  of  which  would  be  seen  dark 
dots.  These  dots  are  the  openings  of  the  gastric  glands.  In 
the  form  of  fine,  wavy  tubes,  the  gastric  glands  are  buried  in 
the  mucous  membrane,  their  mouths  opening  on  the  surface. 
When  the  stomach  is  empty  the  mucous  membrane  is  pale,  but 
when  food  enters,  it  at  once  takes  on  a  rosy  tint.  This  is  due  to 
the  influx  of  blood  from  the  large  number  of  very  minute  blood- 
vessels which  are  in  the  tissue  between  the  rows  of  glands. 

The  cells  of  the  gastric  glands  are  thrown  into  a  state  of 
greater  activity  by  the  increased  quantity  of  blood  supply. 
As  a  result,  soon  after  food  enters  the  stomach,  drops  of  fluid 
collect  ait  the  mouths  of  the  glands  and  trickle  down  its  walls 
to  mix  with  the  food.  Thus  these  glands  produce  a  large 
quantity  of  gastric  juice,  to  aid  in  the  digestion  of  food. 


132 


PRACTICAL    PHYSIOLOGY. 


142.  Digestion  in  the  Stomach.  When  the  food,  thoroughly 
mixed  with  saliva,  reaches  the  stomach,  the  cardiac  end  of  that 
organ  is  closed  as  well  as  the  pyloric 
valve,  and  the  muscular  walls  contract 
on  the  contents.  A  spiral  wave  of  motion 
begins,  becoming  more  rapid  as  diges- 
tion goes  on.  Every  particle  of  food  is 
thus  constantly  churned  about  in  the 
stomach  and  thoroughly  mixed  with  the 
gastric  juice.  The  action  of  the  juice 
is  aided  by  the  heat  of  the  parts,  a 
temperature  of  about  99°  Fahrenheit. 

The  gastric  juice  is  a  thin  almost 
colorless  fluid  with  a  sour  taste  and 
odor.  The  reaction  is  distinctly  acid, 
normally  due  to  free  hydrochloric  acid. 
Its  chief  constituents  are  two  ferments 
called  pepsin  and  rennin,  free  hydro- 
chloric acid,  mineral  salts,  and  95  per 

A  highly  magtifld'  view  of  a    C6nt  °f  Water' 

peptic  or  gastric  gland,  which       Pepsin,  the  important  constituent  of 

is  represented  as  giving  off  .        . 

branches,   it  shows  the  col-  the  gastric  juice,  has  the  power,  in  the 
Presence  of  an  acid,  of  dissolving  the 


duct    D  of    the  gland,  from  proteid    food-Stuffs.       Some    of    which    IS 

which  two  tubes  branch  off.  ,.     , 

Each  tube  is  lined  with  col-  converted  into  what  are  called  peptones, 

umnar  epithelial  ceils  and  b  ^   soluble    and    capable    of   filtering 

there  is  a  minute  central  pas- 

sage with  the  "neck"  at  N.  through  membranes.     The  gastric  juice 

Here  and  there  are  seen  other  .                                                .             .   , 

special  cells  called  parietal  has  no  action  on  starchy  foods,  neither 


does  *  act  on  fats>  except  to  dissolve 
gastric  juice.   The  principal   the   albuminous  walls  of  the  fat  cells. 

cells  are  represented  at  C.  .        ,.  .        .  ,  •        -i       r 

The  fat  itself  is  thus  set  free  in  the  form 

of  minute  globules.  The  whole  contents  of  the  stomach  now 
assume  the  appearance  and  the  consistency  of  a  thick  soup, 
usually  of  a  grayish  color,  known  as  chyme. 


DIGESTION.  133 

It  is  well  known  that  "rennet"  prepared  from  the  calf's 
stomach  has  a  remarkable  effect  in  rapidly  curdling  milk,  and 
this  property  is  utilized  in  the  manufacture  of  cheese.  Now,  a 
similar  ferment  is  abundant  in  the  gastric- juice,  and  may  be 
called  rennin.  It  causes  milk  to  clot,  and  does  this  by  so  acting 
on  the  casein  as  to  make  the  milk  set  into  a  jelly.  Mothers 
are  sometimes  frightened  when  their  children,  seemingly  in 
perfect  health,  vomit  masses  of  curdled  milk.  This  curdling 
of  the  milk  is,  however,  a  normal  process,  and  the  only  note- 
worthy thing  is  its  rejection,  usually  due  to  overfeeding. 

Experiment  58.  To  show  that  pepsin  and  acid  are  necessary  for  gastric 
digestion.  Take  three  beakers,  or  large  test  tubes ;  label  them  A,  B,  C. 
Put  into  A  water  and  a  few  grains  of  powdered  pepsin.  Fill  B  two-thirds 
full  of  dilute  hydrochloric  acid  (one  teaspoonful  to  a  pint),  and  fill  C  two- 
thirds  full  of  hydrochloric  acid  and  a  few  grains  of  pepsin.  Put  into  each 
a  small  quantity  of  well-washed  fibrin,  and  place  them  all  in  a  water  bath  at 
104°  Fahrenheit  for  half  an  hour. 

Examine  them.  In  A,  the  fibrin  is  unchanged ;  in  £,  the  fibrin  is  clear 
and  swollen  up ;  in  C,  it  has  disappeared,  having  first  become  swollen  and 
clear,  and  completely  dissolved,  being  finally  converted  into  peptones. 
Therefore,  both  acid  and  ferment  are  required  for  gastric  digestion. 

Experiment  59.  Half  fill  with  dilute  hydrochloric  acid  three  large  test 
tubes,  labelled  A,  B,  C.  Add  to  each  a  few  grains  of  pepsin.  Boil  B,  and 
make  C  faintly  alkaline  with  sodic  carbonate.  The  alkalinity  may  be 
noted  by  adding  previously  some  neutral  litmus  solution.  Add  to  each  an 
equal  amount  —  a  few  threads  —  of  well-washed  fibrin  which  has  been 
previously  steeped  for  some  time  in  dilute  hydrochloric  acid,  so  that  it  is 
swollen  and  transparent.  Keep  the  tubes  in  a  water-bath  at  about  104° 
Fahrenheit  for  an  hour  and  examine  them  at  intervals  of  twenty  minutes. 

After  five  to  ten  minutes  the  fibrin  in  A  is  dissolved  and  the  fluid  begins 
to  be  turbid.  In  B  and  C  there  is  no  change.  Even  after  long  exposure 
to  100°  Fahrenheit  there  is  no  change  in  B  and  C. 

After  a  variable  time,  from  one  to  four  hours,  the  contents  of 
"the  stomach,  which  are  now  called  chyme,  begin  to  move  on 
in  successive  portions  into  the  next  part  of  the  intestinal  canal. 
The  ring-like  muscles  of  the  pylorus  relax  at  intervals  to  allow 


134  PRACTICAL    PHYSIOLOGY. 

the  muscles  of  the  stomach  to  force  the  partly  digested  mass 
into  the  small  intestines.  This  action  is  frequently  repeated, 
until  even  the  indigestible  masses  which  the  gastric  juice 
cannot  break  down  are  crowded  out  of  the  stomach  into  the 
intestines.  From  three  to  four  hours  after  a  meal  the  stomach 
is  again  quite  emptied. 

A  certain  amount  of  this  semi-liquid  mass,  especially  the 
peptones,  with  any  saccharine  fluids,  resulting  from  the  partial 
conversion  of  starch  or  otherwise,  is  at 
once  absorbed,  making  its  way  through 
the  delicate  vessels  of  the  stomach  into  the 
blood  current,  which  is  flowing  through  the 
gastric  veins  to  the  portal  vein  of  the  liver. 

143.  The  Small  Intestine.  At  the  py- 
loric  end  of  the  stomach  the  alimentary 
canal  becomes  again  a  slender  tube  called 

.;. — ASmallPortion  .,   .  .  .        , 

of  the  MUCOUS  Mem-  the  sma11  intestine.  This  is  about  twenty 
brane  of  the  Small  in-  feet  long  and  one  inch  in  diameter,  and  is 
testine.  (Vilii  are  seen  divided,  for  the  convenience  of  description, 

surrounded    with     the    . 

openings  of  the  tubu-    mt°  three  PartS« 

lar  glands.)  [Magni-  The  first  12  inches  is  called  the  duode- 
fied  20  diameters.]  num>  jnto  tnjs  portion  opens  the  bile  duct 

from  the  liver  with  the  duct  from  the  pancreas,  these  having  been 
first  united  and  then  entering  the  intestine  as  a  common  duct. 

The  next  portion  of  the  intestine  is  called  the  jejunum, 
because  it  is  usually  empty  after  death. 

The  remaining  portion  is  named  the  ileum,  because  of  the 
many  folds  into  which  it  is  thrown.  It  is  the  longest  part  of 
the  small  intestine,  and  terminates  in  the  right  iliac  region, 
opening  into  the  large  intestine.  This  opening  is  guarded  by 
the  folds  of  the  membrane  forming  the  ileo-caecal  valve,  which 
permits  the  passage  of  material  from  the  small  to  the  large 
intestine,  but  prevents  its  backward  movement. 


DIGESTION.  135 

144.  The  Coats  of  the  Small  Intestine.  Like  the  stomach,  the 
small  intestine  has  four  coats,  the  serous,  muscular,  sub-mucous, 
and  mucous.  The  serous  is  the  peritoneum.1  The  muscular  consists 
of  an  outer  layer  of  longitudinal,  and  an  inner  layer  of  circular  fibers, 
by  contraction  of  which  the  food  is  forced  along  the  bowel.  The 
sub-mucous  coat  is  made  up  of  a  loose  layer  of  tissue  in  which  the 
blood-vessels  and  nerves  are  distributed.  The  inner,  or  mucous,  sur- 
face has  a  fine,  velvety  feeling,  due  to  a  countless  number  of  tiny, 
thread-like  projections,  called  villi.  They 
stand  up  somewhat  like  the  "pile"  on 
velvet.  It  is  through  these  villi  that  the 
digested  food  passes  into  the  blood. 

The  inner  coat  of  a  large  part  of  the 
small  intestine  is  thrown  into  numerous 
transverse  folds  called  valvulcz  conni- 

ventes.      These  seem  to  serve  two  pur-     ,, 

FIG.  56.  —  Sectional   View  of 

poses,  to  increase  the  extent  of  the  surface  intestinal  Villi.  (Black  dots 
of  the  bowels  and  to  delay  mechanically  represent  the  glandular  open- 
the  progress  of  the  intestinal  contents.  in8s-) 
Buried  in  the  mucous  layer  throughout  the  length,  both  of  the  small 
and  large  intestines,  are  other  glands  which  secrete  intestinal  fluids. 
Thus,  in  the  lower  part  of  the  ileum  there  are  numerous  glands  in  oval 
patches  known  as  Peyer's  patches.  These  are  very  prone  to  become 
inflamed  and  to  ulcerate  during  the  course  of  typhoid  fever. 

1  The  Peritoneum.  The  intestines  do  not  lie  in  a  loose  mass  in  the  abdominal 
cavity.  Lining  the  walls  of  this  cavity,  just  as  in  a  general  way,  a  paper  lines 
the  walls  of  a  room,  is  a  delicate  serous  membrane,  called  the  peritoneum.  It 
envelops,  in  a  greater  or  less  degree,  all  the  viscera  in  the  cavity  and  forms  folds  by 
which  they  are  connected  with  each  other,  or  are  attached  to  the  posterior  wall.  Its 
arrangement  is  therefore  very  complicated.  When  the  peritoneum  comes  in  con- 
tact with  the  large  intestine,  it  passes  over  it  just  as  the  paper  of  a  room  would  pass 
over  a  gas  pipe  which  ran  along  the  surface  of  the  wall,  and  in  passing  over  it  binds 
it  down  to  the  wall  of  the  cavity.  The  small  intestines  are  suspended  from  the  back 
wall  of  the  cavity  by  a  double  fold  of  the  peritoneum,  called  the  mesentery.  The 
bo'wels  are  also  protected  from  external  cold  by  several  folds  of  this  membrane  loaded 
with  fat.  This  is  known  as  the  great  omentum. 

The  peritoneum,  when  in  health,  secretes  only  enough  fluid  to  keep  its  surface 
lubricated  so  that  the  bowels  may  move  freely  and  smoothly  on  each  other  and  on  the 
other  viscera.  In  disease  this  fluid  may  increase  in  amount,  and  the  abdominal 
cavity  may  become  greatly  distended.  This  is  known  as  ascites  or  dropsy. 


136 


PRACTICAL    PHYSIOLOGY. 


145.  The  Large  Intestine.  The  large  intestine  begins  in 
the  right  iliac  region  and  is  about  five  or  six  feet  long.  It  is 
much  larger  than  the  small  intestine,  joining  it  obliquely  at  a 
short  distance  from  its  end.  A  blind  pouch,  or  dilated  pocket, 
is  thus  formed  at  the  place  of  junction,  called  the  caecum.  A 
valvular  arrangement  called  the  ileo-caecal  valve,  which  is  pro- 
vided with  a  button-hole  slit,  forms  a  kind  of  movable  partition 

between  this  part  of  the  large 
intestine  and  the  small  intestine. 
Attached  to  the  caecum  is  a 
worm-shaped  tube,  about  the  size 
of  a  lead  pencil,  and  from  three 
to  four  inches  long,  called  the 
vermiform  appendix.  Its  use  is 
unknown.  This  tube  is  of  great 
surgical  importance,  from  the  fact 
that  it  is  subject  to  severe  in- 
flammation, often  resulting  in  an 
internal  abscess,  which  is  always 

A,  B,  tubular  glands  seen  in  vertical  sec- 

tion  with  their  orifices  at  c,  opening  dangerous  and  may  prove  fatal. 

upon  the  membrane  between  the  villi;     Inflammation    of    the   appendix  JS 
D,  villus.     (Magnified  40  diameters.)  ... 

known  as  appendicitis,  —  a  name 

quite  familiar  on  account  of  the  many  surgical  operations 
performed  of  late  years  for  its  relief. 

The  large  intestine  passes  upwards  on  the  right  side  as  the 
ascending  colon,  until  the  under  side  of  the  liver  is  reached, 
where  it  passes  to  the  left  side,  as  the  transverse  colon,  below 
the  stomach.  It  there  turns  downward,  as  the  descending 
colon,  and  making  an  S-shaped  curve,  ends  in  the  rectum. 
Thus  the  large  intestine  encircles,  in  the  form  of  a  horseshoe, 
the  convoluted  mass  of  small  intestines. 

Like  the  small  intestine,  the  large  has  four  coats.  The 
mucous  coat,  however,  has  no  folds,  or  villi,  but  numerous 
closely  set  glands,  like  some  of  those  of  the  small  intestine. 


FIG.  57.— Tubular  Glands  of  the 
Small  Intestines. 


DIGESTION.  137 

The  longitudinal  muscular  fibers  of  the  large  intestine  are 
arranged  in  three  bands,  or  bundles,  which,  being  shorter  than 
the  canal  itself,  produce  a  series  of  bulgings  or  pouches  in  its 
walls.  This  sacculation  of  the  large  bowel  is  supposed  to  be 
designed  for  delaying  the  onward  flow  of  its  contents,  thus 
allowing  more  time  for  the  absorption  of  the  liquid  material. 
The  blood-vessels  and  nerves  of  this  part  of  the  digestive  canal 
are  very  numerous,  and  are  derived  from  the  same  sources  as 
those  of  the  small  intestine. 

146.  The  Liver.     The  liver  is  a  part  of  the  digestive  appa- 
ratus, since  it  forms  the  bile,  one  of  the  digestive  fluids.     It  is 
a  large  reddish-brown  organ,  situated  just  below  the  diaphragm, 
and  on  the  right  side.     The  liver  is  the  largest  gland  in  the 
body,  and  weighs  from  50  to  60  ounces.     It  consists  of  two 
lobes,  the  right  and  the  left,  the  right  being  much  the  larger. 
The   upper,  convex   surface  of  the  liver  is  very  smooth  and 
even ;    but  the  under  surface  is  irregular,  broken  by  the  en- 
trance  and  exit  of  the  various  vessels  which  belong  to  the 
organ.     It  is  held  in  its  place  by  five  ligaments,  four  of  which 
are  formed  by  double  folds  of  the  peritoneum. 

The  thin  front  edge  of  the  liver  reaches  just  below  the 
bony  edge  of  the  ribs;  but  the  dome-shaped  diaphragm  rises 
slightly  in  a  horizontal  position,  and  the  liver  passes  up  and  is 
almost  wholly  covered  by  the  ribs.  In  tight  lacing,  the  liver 
is  often  forced  downward  out  from  the  cover  of  the  ribs,  and 
thus  becomes  permanently  displaced.  As  a  result,  other 
organs  in  the  abdomen  and  pelvis  are  crowded  together,  and 
also  become  displaced. 

147.  Minute  Structure  of  the  Liver.     When  a  small  piece 
of  the  liver  is  examined  under  a  microscope  it  is  found  to  be 
made  up  of  masses  of  many-sided  cells,  each  about  T^Vi>  of  an 
inch   in   diameter.      Each    group    of   cells    is   called   a   lobule. 
When  a  single  lobule  is   examined   under  the    microscope  it 


138 


PRACTICAL    PHYSIOLOGY. 


appears  to  be  of  an  irregular,  circular  shape,  with  its  cells 
arranged  in  rows,  radiating  from  the  center  to  the  circumfer- 
ence. Minute,  hair-like  channels  separate  the  cells  one  from 
another,  and  unite  in  one  main  duct  leading  from  the  lobule. 

It  is  the  lobules  which  give  to  the 
liver  its  coarse,  granular  appear- 
ance, when  torn  across. 

Now  there  is  a  large  vessel  called 
the  portal  vein  that  brings  to  the 
liver  blood  full  of  nourishing  ma- 
terial obtained  from  the  stomach 
and  intestines.  On  entering  the 
liver  this  great  vein  conducts  it- 
self as  if  it  were  an  artery.  It 
divides  and  subdivides  into  smaller 
and  smaller  branches,  until,  in  the 
form  of  the  tiniest  vessels,  called 
capillaries,  it  passes  inward  among 


FIG.  58.  —  Diagrammatic  Section 
of  a  Villus. 

A,  layer  of  columnar  epithelium  cover-        ,  n  ,  r     , 

ing  the  villus;    B,  central  lacteal  of  the  Cells  tO  the  Very  Center  of   the 

villus;    C,  unstriped  muscular  fibers  ;  heoatic  lobules 
D,  goblet  cell. 


148.  The  Bile.  We  have  in  the  liver,  on  a  grand  scale, 
exactly  the  same  conditions  as  obtain  in  the  smaller  and 
simpler  glands.  The  thin-walled  liver  cells  take  from  the 
blood  certain  materials  which  they  elaborate  into  an  important 
digestive  fluid,  called  the  bile.1  This  newly  manufactured  fluid 
is  carried  away  in  little  canals,  called  bile  ducts.  These  minute 
ducts  gradually  unite  and  form  at  last  one  main  duct,  which 
carries  the  bile  from  the  liver.  This  is  known  as  the  hepatic 
duct.  It  passes  out  on  the  under  side  of  the  liver,  and  as 

1  The  human  bile  when  fresh  is  generally  of  a  bright  golden  red,  sometimes  of  a 
greenish-yellow  color.  It  becomes  quite  green  when  kept,  and  is  alkaline  in  reaction. 
When  it  has  been  vomited  it  is  distinctly  yellow,  because  of  its  action  on  the  gastric 
juice.  The  bile  contains  a  great  deal  of  coloring  matter ;  and  its  chief  ingredients  are 
two  salts  of  soda,  sodium  taurocholate  and  glycocholate. 


DIGESTION.  1 39 

it  approaches  the  intestine,  it  meets  at  an  acute  angle  the  cystic 
duct  which  proceeds  from  the  gall  bladder  and  forms  with  it 
the  common  bile  duct.  The  common  duct  opens  obliquely 
into  the  horseshoe  bend  of  the  duodenum. 

The  cystic  duct  leads  back  to  the  under  surface  of  the 
liver,  where  it  expands  into  a  sac  capable  of  holding  about 
two  ounces  of  fluid,  and  is  known  as  the  gall  bladder.  Thus 
the  bile,  prepared  in  the  depths  of  the  liver  by  the  liver  cells,  is 
carried  away  by  the  bile  ducts,  and  may  pass  directly  into  the 
intestines  to  mix  with  the  food.  If,  however,  digestion  is  not 
going  on,  the  mouth  of  the  bile  duct  is  closed,  and  in  that 
case  the  bile  is  carried  by  the  cystic  duct  to  the  gall  bladder. 
Here  it  remains  until  such  time  as  it  is  needed. 

149.  Blood  Supply  of  the  Liver.  We  must  not  forget  that 
the  liver  itself,  being  a  large  and  important  organ,  requires  con- 
stant nourishment  for  the  work  assigned  to  it.  The  blood 
which  is  brought  to  it  by  the  portal  vein,  being  venous,  is  not 
fit  to  nourish  it.  The  work  is  done  by  the  arterial  blood 
brought  to  it  by  a  great  branch  direct  from  the  aorta,  known 
as  the  hepatic  artery,  minute  branches  of  which  in  the  form 
of  capillaries,  spread  themselves  around  the  hepatic  lobules. 

The  blood,  having  done  its  work  and  now  laden  with  impuri- 
ties, is  picked  up  by  minute  veinlets,  which  unite  again  and 
again  till  they  at  last  form  one  great  trunk  called  the  hepatic 
vein.  This  carries  the  impure  blood  from  the  liver,  and 
finally  empties  it  into  one  of  the  large  veins  of  the  body. 

After  the  blood  has  been  robbed  of  its  bile-making  materials, 
it  is  collected  by  the  veinlets  that  surround  the  lobules,  and 
finds  its  way  with  other  venous  blood  into  the  hepatic  vein. 
In  brief,  blood  is  brought  to  the  liver  and  distributed  through 
its  substance  by  two  distinct  channels,  — the  portal  vein  and  the 
hepatic  artery,  but  it  leaves  the  liver  by  one  distinct  channel, 
—  the  hepatic  vein. 


140 


PRACTICAL    PHYSIOLOGY. 


150.  Functions  of  the  Liver.  We  have  thus  far  studied 
the  liver  only  as  an  organ  of  secretion,  whose  work  is  to  elabo- 
rate bile  for  future  use  in  the  process  of  digestion.  This  is, 
however,  only  one  of  its  functions,  and  perhaps  not  the  most 


CYSTIC  PORTAL  HEPATIC    ROUND 
ARTERY   VEIN     DUCT    LIGAMENT 


HEPATIC 
ARTERY 


FIG.  59.  —  Showing  the  Relations  of  the  Duodenum  and  Other  Intestinal  Organs. 
(A  portion  of  the  stomach  has  been  cut  away.) 

important.  ,In  fact,  the  functions  of  the  liver  are  not  single, 
but  several.  The  bile  is  not  wholly  a  digestive  fluid,  but 
it  contains,  also,  materials  which  are  separated  from  the  blood 


DIGESTION.  141 

to  be  cast  out  of  the  body  before  they  work  mischief.  Thus,  the 
liver  ranks  above  all  others  as  an  organ  of  excretion,  that  is, 
it  separates  material  of  no  further  use  to  the  body. 

Of  the  various  ingredients  of  the  bile,  only  the  bile  salts  are 
of  use  in  the  work  of  digestion,  for  they  act  upon  the  fats  in  the 
alimentary  canal,  and  aid  somehow  in  their  emulsion  and 
absorption.  They  appear  to  be  themselves  split  up  into  other 
substances,  and  absorbed  with  the  dissolved  fats  into  the 
blood  stream  again. 

The  third  function  of  the  liver  is  very  different  from  those 
already  described.  It  is  found  that  the  liver  of  an  animal  well 
and  regularly  fed,  when  examined  soon  after  death,  contains  a 
quantity  of  a  carbohydrate  substance  not  unlike  starch.  This 
substance,  extracted  in  the  form  of  a  white  powder,  is  really  an 
animal  starch.  It  is  called  glycogen,  or  liver  sugar,  and  is 
easily  converted  into  grape  sugar. 

The  hepatic  cells  appear  to  manufacture  this  glycogen  and 
to  store  it  up  from  the  food  brought  by  the  portal  blood.  It  is 
also  thought  the  glycogen  thus  deposited  and  stored  up  in  the 
liver  is  little  by  little  changed  into  sugar.  Then,  as  it  is  wanted, 
the  liver  disposes  of  this  stored-up  material,  by  pouring  it,  in  a 
state  of  solution,  into  the  hepatic  vein.  It  is  thus  steadily 
carried  to  the  tissues,  as  their  needs  demand,  to  supply  them 
with  material  to  be  transformed  into  heat  and  energy. 

„  151.  The  Pancreas.  The  pancreas,  or  sweetbread,  is  much 
smaller  than  the  liver.  It  is  a  tongue-like  mass  from  six  to 
eight  inches  long,  weighing  from  three  to  four  ounces,  and  is 
often  compared  in  appearance  to  a  dog's  tongue.  It  is  some- 
what the  shape  of  a  hammer  with  the  handle  running  to  a 
point. 

The  pancreas  lies  behind  the  stomach,  across  the  body,  from 
right  to  left,  with  its  large  head  embraced  in  the  horseshoe 
bend  of  the  duodenum.  It  closely  resembles  the  salivary  glands 


142  PRACTICAL    PHYSIOLOGY. 

in  structure,  with  its  main  duct  running  from  one  end  to  the 
other.  This  duct  at  last  enters  the  duodenum  in  company  with 
the  common  bile  duct. 

The  pancreatic  juice,  the  most  powerful  in  the  body,  is  a 
clear,  somewhat  viscid,  fluid.  It  has  a  decided  alkaline  reaction 
and  is  not  unlike  saliva  in  many  respects.  Combined  with  the 
bile,  this  juice  acts  upon  the  large  drops  of  fat  which  pass  from 
the  stomach  into  the  duodenum  and  emulsifies  them.  This 
process  consists  partly  in  producing  a  fine  subdivision  of  the 
particles  of  fat,  called  an  emulsion,  and  partly  in  a  chemical 
decomposition  by  which  a  kind  of  soap  is  formed.  In  this  way 
the  oils  and  fats  are  divided  into  particles  sufficiently  minute  to 
permit  of  their  being  absorbed  into  the  blood. 

Again,  this  most  important  digestive  fluid  produces  on  starch 
an  action  similar  to  that  of  saliva,  but  much  more  powerful.  Dur- 
ing its  short  stay  in  the  mouth,  very  little  starch  is  changed 
into  sugar,  and  in  the  stomach,  as  we  have  seen,  the  action  of 
the  saliva  is  arrested.  Now,  the  pancreatic  juice  takes  up  the 
work  in  the  small  intestine  and  changes  the  greater  part  of  the 
starch  into  sugar.  Nor  is  this  all,  for  it  also  acts  powerfully 

Experiment  60.  To  show  the  action  of  pancreatic  juice  upon  oils  or  fats. 
Put  two  grains  of  Fairchild's  extract  of  pancreas  into  a  four-ounce  bottle. 
Add  half  a  teaspoonful  of  warm  water,  and  shake  well  for  a  few  minutes  ; 
then  add  a  tablespoonful  of  cod  liver  oil ;  shake  vigorously. 

A  creamy,  opaque  mixture  of  the  oil  and  water,  called  an  emulsion,  will 
result.  This  will  gradually  separate  upon  standing,  the  pancreatic  extract 
settling  in  the  water  at  the  bottom.  When  shaken  it  will  again  form  an 
emulsion. 

Experiment  61.  To  show  the  action  of  pancreatic  juice  on  starch.  Put 
two  tablespoonfuls  of  smooth  starch  paste  into  a  goblet,  and  wrhile  still  so 
warm  as  just  to  be  borne  by  the  mouth,  stir  into  it  two  grains  of  the 
extract  of  pancreas.  The  starch  paste  will  rapidly  become  thinner,  and 
gradually  change  into  soluble  starch,  in  a  perfectly  fluid  solution.  Within 
a  few  minutes  some  of  the  starch  is  converted  through  intermediary  stages 
into  maltose.  Use  the  Fehling  test  for  sugar. 


DIGESTION. 


143 


upon  the  proteids  not  acted  upon  in  the  stomach,  and  changes 
them  into  peptones  that  do  not  differ  materially  from  those 
resulting  from  gastric  digestion.  The  remarkable  power  which 
the  pancreatic  juice  possesses  of  acting  on  all  the  food-stuffs 
appears  to  be  due  mainly  to  the  presence  of  a  specific  element 
or  ferment,  known  as  trypsin. 

152.  Digestion  in  the  Small  Intestines.  After  digestion  in 
the  stomach  has  been  going  on  for  some  time,  successive 
portions  of  the  semi-digested  food  begin  to  pass  into  the  duo- 
denum. The  pancreas  now  takes  on  new  activity,  and  a  copi- 
ous flow  of  pancreatic  juice  is  poured  along  its  duct  into  the 


FIG.  60.  —  Diagrammatic  Scheme  of  Intestinal  Absorption. 

A,  mesentery;  B,  lacteals  and  mesentery  glands ;  C,  veins  of  intestines;  R.C,  receptacle  of 
the  chyle  (receptaculum  chyli) ;  P.V,  portal  vein;  H.V,  hepatic  veins;  S.V.C,  superior 
vena  cava  ;  R.A,  right  auricle  of  the  heart ;  I.V.C,  inferior  vena  cava. 

'intestines.  As  the  food  is  pushed  along  over  the  common 
opening  of  the  bile  and  pancreatic  ducts,  a  great  quantity  of 
bile  from  this  reservoir,  the  gall  bladder,  is  poured  into  the 
intestines.  These  two  digestive  fluids  are  now  mixed  with  the 
chyme,  and  act  upon  it  in  the  remarkable  manner  just  described. 
The  inner  surface  of  the  small  intestine  also  secretes  a  liquid 
called  intestinal  juice,  the  precise  functions  of  which  are  not 
known.  The  chyme,  thus  acted  upon  by  the  different  digestive 
fluids,  resembles  a  thick  cream,  and  is  now  called  chyle.  The 
chyle  is  propelled  along  the  intestine  by  the  worm-like  contrac- 


144  PRACTICAL    PHYSIOLOGY. 

tions  of  its  muscular  walls.  A  function  of  the  bile,  not  yet 
mentioned,  is  to  stimulate  these  movements,  and  at  the  same 
time  by  its  antiseptic  properties  to  prevent  putrefaction  of  the 
contents  of  the  intestine. 

i53»  Digestion  in  the  Large  Intestines.  Digestion  does 
not  occur  to  any  great  extent  in  the  large  intestines.  The  food 
enters  this  portion  of  the  digestive  canal  through  the  ileo- 
caecal  valve,  and  travels  through  it  slowly.  Time  is  thus  given 
for  the  fluid  materials  to  be  taken  up  by  the  blood-vessels  of 
the  mucous  membrane.  The  remains  of  the  food  now  become 
less  fluid,  and  consist  of  undigested  matter  which  has  escaped 
the  action  of  the  several  digestive  juices,  or  withstood  their 
influence.  Driven  onward  by  the  contractions  of  the  muscular 
walls,  the  refuse  materials  at  last  reach  the  rectum,  from  which 
they  are  voluntarily  expelled  from  the  body. 

ABSORPTION. 

154.  Absorption.  While  food  remains  within  the  alimentary 
canal  it  is  as  much  outside  of  the  body,  so  far  as  nutrition  is 
concerned,  as  if  it  had  never  been  taken  inside.  To  be  of  any 
service  the  food  must  enter  the  blood  ;  it  must  be  absorbed. 
The  efficient  agents  in  absorption  are  the  blood-vessels,  the 
lacteals,  and  the  lymphatics.  The  process  through  which  the 
nutritious  material  is  fitted  to  enter  the  blood,  is  called  absorp- 
tion. It  is  a  process  not  confined,  as  we  shall  see,  simply  to 
the  alimentary  canal,  but  one  that  is  going  on  in  every  tissue. 

The  vessels  by  which  the  process  of  absorption  is  carried  on 
are  called  absorbents.  The  story,  briefly  told,  is  this  :  certain 
.food  materials  that  have  been  prepared  to  enter  the  blood, 
filter  through  the  mucous  membrane  of  the  intestinal  canal, 
and  also  the  thin  walls  of  minute  blood-vessels  and  lymphatics, 
and  are  carried  by  these  to  larger  vessels,  and  at  last  i^ach  the 
heart,  thence  to  be  distributed  to  the  tissues. 


DIGESTION.  145 

155.  Absorption  from  the  Mouth  and  Stomach.    The  lining 
of  the  mouth  and  oesophagus  is  not  well  adapted  for  absorption. 
That  this  does  occur  is  shown  by  the  fact  that  certain  poisonous 
chemicals,  like  cyanide  of  potash,  if  kept  in  the  mouth  for  a 
few  moments  will  cause  death.     While  we  are  chewing  and 
swallowing  our  food,  no  doubt  a  certain  amount  of  water  and 
common  salt,  together  with  sugar  which  has  been  changed  from 
starch  by  the  action  of  the  saliva,  gains  entrance  to  the  blood. 

In  the  stomach,  however,  absorption  takes  place  with  great 
activity.  The  semi-liquid  food  is  separated  from  the  enormous 
supply  of  blood-vessels  in  the  mucous  membrane  only  by  a  thin 
porous  partition.  There  is,  therefore,  nothing  to  prevent  the 
exchange  taking  place  between  the  blood  and  the  food.  Water, 
along  with  any  substances  in  the  food  that  have  become  dis- 
solved, will  pass  through  the  partition  and  enter  the  blood- 
current.  Thus  it  is  that  a  certain  amount  of  starch  that  has 
been  changed  into  sugar,  of  salts  in  solution,  of  proteids  con- 
verted into  peptones,  is  taken  up  directly  by  the  blood-vessels 
of  the  stomach. 

156.  Absorption  by  the  Intestines.     Absorption   by  the 
intestines   is   a   most    active   and   complicated  process.     The 
stomach   is  really  an  organ  more  for  the  digestion  than  the 
absorption   of  food,   while  the  small  intestines  are  especially 
constructed  for  absorption.     In  fact,  the  greatest  part  of  absorp- 
tion is  accomplished  by  the  small  intestines.     They  have  not 
only  a  very  large  area  of  absorbing  surface,  but  also  structures 
especially  adapted  to  do  this  work. 

157.  The  Lacteals.     We  have  learned  in  Section  144  that 
the  mucous  lining  of  the  small  intestines  is  crowded  with  mil- 
lions of  little  appendages  called  villi,  meaning  "tufts  of  hair." 
These  are  only  about  -fa  of  an  inch  long,  and  a  dime  will  cover 
more  tl^an  five  hundred  of  them.     Each  villus  contains  a  loop  of 
blood-vessels,  and  another  vessel,  the  lacteal,  so  called  from  the 


146  PRACTICAL    PHYSIOLOGY. 

Latin  word  lac,  milk,  because  of  the  milky  appearance  of  the  fluid 
it  contains.  The  villi  are  adapted  especially  for  the  absorp- 
tion of  fat.  They  dip  like  the  tiniest  ringers  into  the  chyle, 
and  the  minute  particles  of  fat  pass  through  their  cellular 
covering  and  gain  entrance  to  the  lacteals.  The  milky  material 
sucked  up  by  the  lacteals  is  not  in  a  proper  condition  to  be 
poured  at  once  into  the  blood  current.  It  is,  as  it  were,  in  too 
crude  a  state,  and  needs  some  special  preparation. 

The  intestines  are  suspended  to  the  posterior  wall  of  the 
abdomen  by  a  double  fold  of  peritoneum  called  the  mesentery. 
In  this  membrane  are  some  150  glands  about  the  size  of  an 
almond,  called  mesenteric  glands.  Now  the  lacteals  join  these 
glands  and  pour  in  their  fluid  contents  to  undergo  some  impor- 
tant changes.  It  is  not  unlikely  that  the  mesenteric  glands 
may  intercept,  like  a  filter,  material  which,  if  allowed  to  enter 
the  blood,  would  disturb  the  whole  body.  Thus,  while  the 
glands  might  suffer,  the  rest  of  the  body  might  escape.  This 
may  account  for  the  fact  that  these  glands  and  the  lymphatics 
may  be  easily  irritated  and  inflamed,  thus  becoming  enlarged 
and  sensitive,  as  often  occurs  in  the  axilla. 

Having  been  acted  upon  by  the  mesenteric  glands,  and 
passed  through  them,  the  chyle  flows  onward  until  it  is  poured 
into  a  dilated  reservoir  for  the  chyle,  known  as  the  recepta- 
culum  chyli.  "  This  is  a  sac-like  expansion  of  the  lower  end  of 
the  thoracic  duct.  Into  this  receptacle,  situated  at  the  level  of 
the  upper  lumbar  vertebrae,  in  front  of  the  spinal  column,  are 
poured,  not  only  the  contents  of  the  lacteals,  but  also  of  the 
lymphatic  vessels  of  the  lower  limbs. 

158.  The  Thoracic  Duct.  This  duct  is  a  tube  from  fifteen 
to  eighteen  inches  long,  which  passes  upwards  in  front  of  the 
spine  to  reach  the  base  of  the  neck,  where  it  opens  at  the 
junction  of  the  great  veins  of  the  left  side  of  the  head  with 
those  of  the  left  arm.  Thus  the  thoracic  duct  acts  as  a  kind 


DIGESTION. 


147 


of  feeding  pipe  to  carry  along  the  nutritive  material  obtained 
from  the  food  and  to  pour  it  into  the  blood  current.  It  is  to  be 
remembered  that  the  lacteals  are  in  reality  lymphatics  —  the 
lymphatics  of  the  intestines. 

159.  The  Lymphatics.  In  nearly  every  tissue  and  organ  of 
the  body  there  is  a  marvelous  network  of  vessels,  precisely  like 
the  lacteals,  called  the 
lymphatics.  These  are 
busily  at  work  taking  up 
and  making  over  anew 
waste  fluids  or  surplus 
materials  derived  from 
the  blood  and  tissues 
generally.  It  is  esti- 
mated that  the  quantity 
of  fluid  picked  up  from 
the  tissues  by  the  lym- 
phatics and  restored 
daily  to  the  circulation 
is  equal  to  the  bulk  of 
the  blood  in  the  body. 
The  lymphatics  seem  to 
start  out  from  the  part 
in  which  they  are  found,  like  the  rootlets  of  a  plant  in  the  soil. 
They  carry  a  turbid,  slightly  yellowish  fluid,  called  lymph,  very 
much  like  blood  without  the  red  corpuscles. 

Now,  just  as  the  chyle  was  not  fit  to  be  immediately  taken 
up  by  the  blood,  but  was  passed  through  the  mesenteric  glands 
to  be  properly  worked  over,  so  the  lymph  is  carried  to  the 
lymphatic  glands,  where  it  undergoes  certain  changes  to  fit  it 
for  being  poured  into  the  blood.  Nature,  like  a  careful  house- 
keeper, allows  nothing  to  be  wasted  that  can  be  of  any  further 
service  in  the  animal  economy  (Figs.  63  and  64). 


FIG.  61.  —  Section  of  a  Lymphatic  Gland. 

strong  fibrous  capsule  sending  partitions  into  the 
gland;  B,  partitions  between  the  follicles  or 
pouches  of  the  cortical  or  outer  portion  ;  C,  par- 
titions of  the  medullary  or  central  portion  ;  D,  E, 
.masses  of  protoplasmic  matter  in  the  pouches  of 
the  gland;  F,  lymph-vessels  which  bring  lymph  to 
the  gland,  passing  into  its  center;  G,  confluence 
of  those  leading  to  the  efferent  vessel ;  H ,  vessel 
which  carries  the  lymph  away  from  the  gland. 


148  PRACTICAL    PHYSIOLOGY. 

The  lymphatics  unite  to  form  larger  and  larger  vessels,  and 
at  last  join  the  thoracic  duct,  except  the  lymphatics  of  the 
right  side  of  the  head  and  chest  and  right  arm.  These  open 
by  the  right  lymphatic  duct  into  the  venous  system  on  the 
right  side  of  the  neck. 

The  whole  lymphatic  system  may  be  regarded  as  a  necessary 
appendage  to  the  vascular  system  (Chapter  VII.).  It  is  conven- 
ient, however,  to  treat  it  under  the  general  topic  of  absorption, 
in  order  to  complete  the  history  of  food  digestion. 

160.  The  Spleen  and  Other  Ductless  Glands.  With  the  lym- 
phatics may  be  classified,  for  convenience,  a  number  of  organs  called 
ductless  or  blood  glands.  Although  they  apparently  prepare  mate- 
rials for  use  in  the  body,  they  have  no  ducts  or  canals  along  which 
may  be  carried  the  result  of  their  work.  Again,  they  are  called 
blood  glands  because  it  is  supposed  they  serve  some  purpose  in  pre- 
paring material  for  the  blood. 

The  spleen  is  the  largest  of  these  glands.  It  lies  beneath  the  dia- 
phragm, and  upon  the  left  side  of  the  stomach.  It  is  of  a  deep  red  color, 
full  of  blood,  and  is  about  the  size  and  shape  of  the  palm  of  the  hand. 

The  spleen  has  a  fibrous  capsule  from  which  partitions  pass  in- 
wards, dividing  it  into  spaces  by  a  framework  of  elastic  tissue,  with 
plain  muscular  fibers.  These  spaces  are  filled  with  what  is  called 
the  spleen  pulp,  through  which  the  blood  filters  from  its  artery,  just 
as  a  fluid  would  pass  through  a  sponge.  The  functions  of  the  spleen 
are  not  known.  It  appears  to  take  some  part  in  the  formation  of 
blood  corpuscles.  In  certain  diseases,  like  malarial  fever,  it  may  be- 
come remarkably  enlarged.  It  may  be  wholly  removed  from  an 
animal  without  apparent  injury.  During  digestion  it  seems  to  act  as 
a  muscular  pump,  drawing  the  blood  onwards  with  increased  vigor 
along  its  large  vein  to  the  liver. 

The  thyroid  is  another  ductless  gland.  It  is  situated  beneath  the 
muscles  of  the  neck  on  the  sides  of  "  Adam's  apple  "  and  below  it. 
It  undergoes  great  enlargement  in  the  disease  called  goitre. 

The  thymus  is  also  a  blood  gland.  It  is  situated  around  the  wind- 
pipe, behind  the  upper  part  of  the  breastbone.  Until  about  the  end 
of  the  second  year  it  increases  in  size,  and  then  it  begins  gradually  to 


DIGESTION. 


149 


shrivel  away.  Like  the  spleen,  the  thyroid  and  thymus  glands  are  sup- 
posed to  work  some  change  in  the  blood,  but  what  is  not  clearly  known. 
The  suprarenal  capsules  are  two  little  bodies,  one  perched  on  the  top 
of  each  kidney,  in  shape  not  unlike  that  of  a  conical  hat.  Of  their 
functions  nothing  definite  is  known. 


EXPERIMENTS. 

The  action  produced  by  the  tendency  of  fluids  to  mix,  or  become  equally 
diffused  in  contact  with  each  other,  is  known  as  osmosis,  a  form  of  mole- 
cular attraction  allied  to  that  of  adhesion.  The  various  physical  processes 
by  which  the  products  of  digestion  are  transferred  from  the  digestive  canal 
to  the  blood  may  be  illustrated  in  a  general  way  by 
the  following  simple  experiments. 

The  student  must,  however,  understand  that  the 
necessarily  crude  experiments  of  the  classroom  may 
not  conform  in  certain  essentials  to  these  great  pro- 
cesses conducted  in  the  living  body,  which  they  are 
intended  to  illustrate  and  explain. 

Experiment  62.  Simple  Apparatus  for  Illustrating 
Endosmotic  Action.  "  Remove  carefully  a  circular  por- 
tion, about  an  inch  in  diameter,  of  the  shell  from  one 
end  of  an  egg,  which  may  be  done  without  injuring  the 
membranes,  by  cracking  the  shell  in  small  pieces,  which 
are  picked  off  with  forceps.  A  small  glass  tube  is  then 
introduced  through  an  opening  in  the  shell  and  mem- 
branes of  the  other  end  of  the  egg,  and  is  secured  in  a 
vertical  position  by  wax  or  plaster  of  Paris,  the  tube 
penetrating  the  yelk.  The  egg  is  then  placed  in  a 
wine-glass  partly  filled  with  water.  In  the  course  of  a 
few  minutes,  the  water  will  have  penetrated  the  ex- 
posed membrane,  and  the  yelk  will  rise  in  the  tube."  — 
FLINT'S  Human  Physiology,  page  293. 


FIG.  62. 


Experiment  63.  Stretch  a  piece  of  moist  bladder  across  a  glass  tube, — 
a  common  lamp-chimney  will  do.  Into  this  put  a  strong  saline  solution. 
Now  suspend  the  tube  in  a  wide-mouthed  vessel  of  water.  After  a  short 
time  it  will  be  found  that  a  part  of  the  salt  solution  has  passed  through  into 
the  water,  while  a  larger  amount  of  water  has  passed  into  the  tube  and 
raised  the  height  of  the  liquid  within  it. 


I5O  PRACTICAL    PHYSIOLOGY. 

161.  The  Quantity  of  Food  as  Affected  by  Age.  The 
quantity  of  food  required  to  keep  the  body  in  proper  condition 
is  modified  to  a  great  extent  by  circumstances.  Age,  occupa- 
tion, place  of  residence,  climate,  and  season,  as  well  as  individ- 
ual conditions  of  health  and  disease,  are  always  important 
factors  in  the  problem.  In  youth  the  body  is  not  only  growing, 
but  the  tissue  changes  are  active.  The  restless  energy  and 
necessary  growth  at  this  time  of  life  cannot  be  maintained  with- 
out an  abundance  of  wholesome  food.  This  food  supply  for 
young  people  should  be  ample  enough  to  answer  the  demands 
of  their  keen  appetite  and  vigorous  digestion. 

In  adult  life,  when  the  processes  of  digestion  and  assimila- 
tion are  active,  the  amount  of  food  may  without  harm,  be  in 
excess  of  the  actual  needs  of  the  body.  This  is  true,  how- 
ever, only  so  long  as  active  muscular  exercise  is  taken. 

In  advanced  life  the  tissue  changes  are  slow,  digestion  is  less 
active,  and  the  ability  to  assimilate  food  is  greatly  diminished. 
Growth  has  ceased,  the  energy  which  induced  activity  is  gone, 
and  the  proteids  are  no  longer  required  to  build  up  worn-out 
tissues.  Hence,  as  old  age  approaches,  the  quantity  of  nitro- 
genous foods  should  be  steadily  diminished. 

Experiment  64.  Obtain  a  sheep's  bladder  and  pour  into  it  a  heavy 
solution  of  sugar  or  some  colored  simple  elixir,  found  at  any  drug  store. 
Tie  the  bladder  carefully  and  place  it  in  a  vessel  containing  water.  After  a 
while  it  will  be  found  that  an  interchange  has  occurred,  water  having  passed 
into  the  bladder  and  the  water  outside  having  become  sweet. 

Experiment  65.  Make  a  hole  about  as  big  as  a  five-cent  piece  in  the 
large  end  of  an  egg.  That  is,  break  the  shell  carefully  and  snip  the  outer 
shell  membrane,  thus  opening  the  space  between  the  outer  and  inner  mem- 
branes. Now  put  the  egg  into  a  glass  of  water,  keeping  it  in  an  upright 
position  by  resting  on  a  napkin-ring.  There  is  only  the  inner  shell  membrane 
between  the  liquid  white  of  the  egg  (albumen)  and  the  water. 

An  interchange  takes  place,  and  the  water  passes  towards  the  albumen. 
As  the  albumen  does  not  pass  out  freely  towards  the  water,  the  membrane 
becomes  distended,  like  a  little  bag  at  the  top  of  the  egg. 


DIGESTION.  I  5  I 

162.  Ill  Effects  of  a  too  Generous  Diet.     A  generous  diet, 
even  of  those  who  take  active  muscular  exercise,  should  be 
indulged  in  only  with  vigilance  and  discretion.     Frequent  sick 
or  nervous  headaches,  a  sense  of  fullness,  bilious  attacks,  and 
dyspepsia   are   some  of  the  after-effects  of  eating  more  food 
than  the  body  actually  requires.     The  excess  of  food  is  not 
properly  acted  upon  by  the  digestive  juices,  and  is  liable  to 
undergo  fermentation,  and  thus  to  become  a  source  of  irritation 
to  the  stomach  and  the  intestines.     If  too  much  and  too  rich 
food  be  persistently  indulged  in,  the  complexion  is  apt  to  become 
muddy,  the  skin,  especially  of  the  face,  pale  and  sallow,  and 
more  or  less  covered  with  blotches  and  pimples  ;  the  breath  has 
an  unpleasant  odor,  and  the  general  appearance  of  the  body  is 
unwholesome. 

An  excess  of  any  one  of  the  different  classes  of  foods  may 
lead  to  serious  results.  Thus  a  diet  habitually  too  rich  in 
proteids,  as  with  those  who  eat  meat  in  excess,  often  over- 
taxes the  kidneys  to  get  rid  of  the  excess  of  nitrogenous  waste, 
and  the  organs  of  excretion  are 'not  able  to  rid  the  tissues  of 
waste  products  which  accumulate  in  the  system.  From  the 
blood,  thus  imperfectly  purified,  may  result  kidney  troubles 
and  various  diseases  of  the  liver  and  the  stomach. 

163.  Effect  of  Occupation.     Occupation  has  an  important 
influence  upon  the  quantity  of  food  demanded  for  the  bodily 
support.     Those  who  work  long  and  hard  at  physical  labor, 
need  a  generous  amount  of  nutritious  food.     A  liberal  diet  of 
the  cereals  and  lean  meat,  especially  beef,  gives  that  vigor  to 
the  muscles  which  enables  one  to  undergo  laborious  and  pro- 
longed physical  exertion.     On  the  other  hand,  those  who  follow 
a  sedentary  occupation  do  not  need  so  large  a  quantity  of  food. 
Brain-workers  who  would  work  well  and  live  long,  should  not 
indulge  in  too  generous  a  diet.     The  digestion  of  heavy  meals 
involves  a  great  expenditure  of  nervous  force.     Hence,  the 


152 


PRACTICAL    PHYSIOLOGY. 


forces  of  the  brain-worker,  being  required  for  mental  exertion, 
should  not  be  expended  to  an  unwarranted  extent  on  the  task 
of  digestion. 

164.  Effect  of  Climate.     Climate  also  has  a  marked  influence  on 
the  quantity  of  food  demanded  by  the  system.     Much  more  food  of 
all  kinds  is  consumed  in  cold  than  in  warm  climates.     The  accounts 
by  travelers  of  the  quantity  of  food  used  by  the  inhabitants  of  the 
frigid  zone  are  almost  beyond  belief.     A  Russian  admiral  gives  an 

instance  of  a  man  who,  in  his  pres- 
ence, ate  at  a  single  meal  28  pounds 
of  rice  and  butter.  Dr.  Hayes,  tte 
Arctic  traveler,  states  from  personal 
observation  that  the  daily  ration  of 
the  Eskimos  is  1 2  to  15  pounds  of 
meat.  With  the  thermometer  rang- 
ing from  60  to  70°  F.  below  zero, 
there  was  a  persistent  craving  for 
strong  animal  diet,  especially  fatty 
foods.1 

The  intense  cold  makes  such  a 
drain  upon  the  heat-producing  power 
of  the  body  that  only  food  contain- 
ing the  largest  proportion  of  carbon 
is  capable  of  making  up  for  the  loss. 

In  tropical  countries,  on  the  other  hand,  the  natives  crave  and  subsist 

mainly  upon  fruits  and  vegetables. 

165.  The  Kinds  of  Food  Required.     An  appetite  for  plain, 
well-cooked  food  is  a  safe  guide  to  follow.     Every  person  in 
good  health,  taking  a  moderate  amount  of  daily  exercise,  should 
have  a  keen  appetite  for  three  meals  a  day  and  enjoy  them. 
Food  should  be  both  nutritious  and  digestible.     It  is  nutritious 
in  proportion  to  the  amount  of  material  it  furnishes  for  the 
nourishment  of  the  tissues.     It  is  digestible  in  a  greater  or 
less  degree  in  respect  to  the  readiness  with  which  it  yields  to 

1  Nansen  emphasizes  this  point  in  his  recently  published  work,  Farthest  North. 


FIG.  63.  —  Lymphatics  and  Lym- 
phatic Glands  of  the  Axilla. 


DIGESTION.  153 

the  action  of  the  digestive  fluids,  and  is  prepared  to  be  taken 
up  by  the  blood.  This  digestibility  depends  partly  upon  the 
nature  of  the  food  in  its  raw  state,  partly  upon  the  effect 
produced  upon  it  by  cooking,  and  to  some  extent  upon  its 
admixture  with  other  foods.  Certain  foods,  as  the  vegetable 
albumens,  are  both  nutritious  and  digestible.  A  hard-working 
man  may  grow  strong  and  maintain  vigorous  health  on  most  of 
them,  even  if  deprived  of  animal  food. 

While  it  is  true  that  the  vegetable  albumens  furnish  all  that 
is  really  needed  for  the  bodily  health,  animal  food  of  some 
kind  is  an  economical  and  useful  addition  to  the  diet.  Races 
of  men  who  endure  prolonged  physical  exertion  have  dis- 
covered for  themselves,  without  the  teaching  of  science,  the 
great  value  of  meat.  Hence  the  common  custom  of  eating 
meat  with  bread  and  vegetables  is  a  sound  one.  It  is  un- 
doubtedly true  that  the  people  of  this  country,  as  a  rule,  eat 
meat  too  often  and  too  much  at  a  time.  The  judicious  admix- 
ture of  different  classes  of  foods  greatly  aids  their  digestibility. 

The  great  abundance  and  variety  of  food  in  this  country, 
permit  this  principle  to  be  put  into  practice.  A  variety  of 
mixed  foods,  as  milk,  eggs,  bread,  and  meat,  are  almost  inva- 
riably associated  to  a  greater  or  less  extent  at  every  meal. 

Oftentimes  where  there  is  of  necessity  a  sameness  of  diet, 
there  arises  a  craving  for  special  articles  of  food.  Thus  on 
long  voyages,  and  during  long  campaigns  in  war,  there  is  an 
almost  universal  craving  for  onions,  raw  potatoes,  and  other 
vegetables. 

166.  Hints  about  Meals.  On  an  average,  three  meals 
each  day,  from  five  to  six  hours  apart,  is  the  proper  number 
for  adults.  Five  hours  is  by  no  means  too  long  a  time  to  in- 
tervene between  consecutive  meals,  for  it  is  not  desirable  to 
introduce  new  food  into  the  stomach,  until  the  gastric  diges- 
tion of  the  preceding  meal  has  been  completed,  and  until  the 


154  PRACTICAL    PHYSIOLOGY. 

stomach  has  had  time  to  rest,  and  is  in  condition  to  receive 
fresh  material.  The  stomach,  like  other  organs,  does  its  work 
best  at  regular  periods.1 

Eating  out  of  mealtimes  should  be  strictly  avoided,  for  it 
robs  the  stomach  of  its  needed  rest.  Food  eaten  when  the 
body  and  mind  are  wearied  is  not  well  digested.  Rest,  even 
for  a  few  minutes,  should  be  taken  before  eating  a  full  meal. 
It  is  well  to  lie  down,  or  sit  quietly  and  read,  fifteen  minutes 
before  eating,  and  directly  afterwards,  if  possible. 

Severe  exercise  and  hard  study  just  after  a  full  meal,  are 
very  apt  to  delay  or  actually  arrest  digestion,  for  after  eating 
heartily,  the  vital  forces  of  the  body  are  called  upon  to  help  the 
stomach  digest  its  food.  If  our  bodily  energies  are  compelled, 
in  addition  to  this,  to  help  the  muscles  or  brain,  digestion  is 
retarded,  and  a  feeling  of  dullness  and  heaviness  follows. 
Fermentative  changes,  instead  of  the  normal  digestive  changes, 
are  apt  to  take  place  in  the  food. 

167.  Practical  Points  about  Eating.  We  should  not  eat 
for  at  least  two  or  three  hours  before  going  to  bed.  When  we 
are  asleep,  the  vital  forces  are  at  a  low  ebb,  the  process  of  diges- 
tion is  for  the  time  nearly  suspended,  and  the  retention  of 
incompletely  digested  food  in  the  stomach  may  cause  bad 
dreams  and  troubled  sleep.  But  in  many  cases  of  sleeplessness, 
a  trifle  of  some  simple  food,  especially  if  the  stomach  seems  to 
feel  exhausted,  often  appears  to  promote  sleep  and  rest. 

1  We  should  make  it  a  point  not  to  omit  a  meal  unless  forced  to  do  so. 
Children,  and  even  adults,  often  have  the  habit  of  going  to  school  or  to  work  in  a 
hurry,  without  eating  any  breakfast.  There  is  almest  sure  to  be  a  fainting,  or  "  all- 
gone  "  feeling  at  the  stomach  before  another  mealtime.  This  habit  is  injurious,  and 
sure  to  produce  pernicious  results. 

NOTE.  The  table  on  the  next  page  shows  the  results  of  many  experiments  to 
illustrate  the  time  taken  for  the  gastric  digestion  of  a  number  of  the  more  common 
solid  foods.  There  are  a  good  many  factors  of  which  the  table  takes  no  account, 
such  as  the  interval  since  the  last  meal,  state  of  the  appetite,  amount  of  work  and 
exercise,  method  of  cooking,  and  especially  the  quantity  of  food. 


TABLE   SHOWING  THE   DIGESTIBILITY  OF  THE   MORE 
COMMON   SOLID   FOODS. 


FOOD. 

How 
COOKED. 

TIME  IN 
STOMACH. 
HOURS. 

FOOD. 

How 

COOKED. 

TIME  IN 
STOMACH. 
HOURS. 

Apples,  sweet  and  mel- 
low      

Raw 

ii 

Milk    

Raw 

2i 

Apples,  sour  and  hard  . 
Apple  dumpling     .     . 
Bass,  striped,  fresh 
Beans,  pod     .... 
Beef,  with  salt  only 
"     fresh,  lean.     .     . 

u           u          ti 

"     old,  hard,  salted  . 
Beefsteak 

Boiled 
Broiled 
Boiled 

Raw 
Fried 
Roasted 
Boiled 
Broiled 

4 
3 
3 
4 

2| 

3 
4 
3* 
4| 

? 

Mutton,  fresh    .     .    . 

a            u 
«            « 

Oysters,  fresh    .     /    . 

U                  11 

Parsnips  
Pig  • 

Pig's  feet,  soused  .    . 
Pork  recently  salted 

Broiled 
Boiled 
Roasted 
Raw 
Roasted 
Stewed 
Boiled 
Roasted 
Boiled 
u 

3 
3 

3i 

4 

34 

3* 

*4 

4 
i 

,1 

Beets     

Boiled 

sl 

u 

Fried 

42 

4* 

Bread,  corn    .... 

Baked 

1± 

it 

Raw 

"        wheat,  fresh     . 
Butter             .         .     . 

Melted 

34 

«i 

"       steaks    .     .     . 

Fried 
Stewed 

3* 

Cabbage,  with  vinegar 

«           it           a 

"       heads.    .    . 
Carrots 

Raw 

Boiled 
Raw 
Boiled 

2 

44 

4 

41 

"       fat  or  lean  .    . 
Potatoes  

H 

tl 

Roasted 
Baked 
Boiled 

5i 
^i 

34 
2i 

Cheese,  old,  strong  .    . 
Chicken,  full-grown 
"        soup    .    .    . 
Codfish,  cured,  dried  . 
Corncake  . 

Raw 

Fricassee 
Boiled 

u 

Baked 

34 

2| 

3 

2 
2f 

Rice     
Sago    
Salmon,  salted  .     .     . 
Soup,  barley  .... 
"     beans 

Boiled 

u 
u 
It 

H 

*a 

'f 

4 

4 

Custard 

2! 

u     beef  vegetables 

3 

Duck,  domestic  .     .     . 
"     wild     .... 
Eggs,  fresh,  whipped  . 

it 

Roasted 

« 

Raw 

M 

4 
44 
4 

2 

bread     .     .     . 
"     marrow  bone    . 
"      mutton     .     .     . 

• 
a 
H 
RaVpH 

4 

4 

34 
,1 

"     soft-boiled     .    . 
"     hard-boiled   .    . 

Boiled 

u 

Fried 

3 
34 
•*i 

Suet,  beef,  fresh     .    . 
"     mutton      .     .     . 
Tapioca 

Boiled 
u 

22 

Si 

44 

Fowl,  domestic  .     .     . 
Gelatin.    .    .    .    '.    '. 

Boiled 
Roasted 
Boiled 

4 
4 

2^ 

Tripe,  soused    .    .    . 
Trout,  salmon,  fresh  . 

u          a            « 

ti 
u 
Fried 

«* 

Ti 

Goose   

Roasted 

2i 

Roasted 

1^ 

yl 

Green  corn  and  beans  . 
Hash,  meat  and  vege- 
tables      

Boiled 
Warmed 

3l 

2i 

"      domestic   .    . 

a            a 

Turnips    

Boiled 
Roasted 
Boiled 

2t 

«i 

4 
*i 

Lamb    

Broiled 

2i 

Veal 

Roasted 

J2 

Liver     

u 

Fried 

4 

,1 

Milk      

Boiled 

RrnilpH 

45 

ti 

Jf 

156  PRACTICAL    PHYSIOLOGY. 

The  state  of  mind  has  much  to  do  with  digestion.  Sudden 
fear  or  joy,  or  unexpected  news,  may  destroy  the  appetite  at 
once.  Let  a  hungry  person  be  anxiously  awaiting  a  hearty 
meal,  when  suddenly  a  disastrous  telegram  is  brought  him  ;  all 
appetite  instantly  disappears,  and  the  tempting  food  is  refused. 
Hence  we  should  laugh  and  talk  at  our  meals,  and  drive  away 
anxious  thoughts  and  unpleasant  topics  of  discussion. 

The  proper  chewing  of  the  food  is  an  important  element  in 
digestion.  Hence,  eat  slowly,  and  do  not  "bolt"  large  frag- 
ments of  food.  If  imperfectly  chewed,  it  is  not  readily  acted 
upon  by  the  gastric  juice,  and  often  undergoes  fermentative 
changes  which  result  in  sour  stomach,  gastric  pain,  and  other 
digestive  disturbance. 

If  we  take  too  much  drink  with  our  meals,  the  flow  of  the 
saliva  is  checked,  and  digestion  is  hindered.  It  is  not  desir- 
able to  dilute  the  gastric  juice,  nor  to  chill  the  stomach  with  a 
large  amount  of  cold  liquid. 

Do  not  take  food  and  drink  too  hot  or  too  cold.  If  they  are 
taken  too  cold,  the  stomach  is  chilled,  and  digestion  delayed. 
If  we  drink  freely  of  ice-water,  it  may  require  half  an  hour 
or  more  for  the  stomach  to  regain  its  natural  heat. 

It  is  a  poor  plan  to  stimulate  a  flagging  appetite  with  highly 
spiced  food  and  bitter  drinks.  An  undue  amount  of  pepper, 
mustard,  horseradish,  pickles,  and  highly  seasoned  meat-sauces 
may  stimulate  digestion  for  the  time,  but  they  soon  impair  it. 

NOTE.  The  process  of  gastric  digestion  was  studied  many  years  ago  by  Dr.  Beau- 
mont and  others,  in  the  remarkable  case  of  Alexis  St.  Martin,  a  French-Canadian, 
who  met  with  a  gun-shot  wound  which  left  a  permanent  opening  into  his  stomach, 
guarded  by  a  little  valve  of  mucous  membrane.  Through  this  opening  the  lining  of 
the  stomach  could  be  seen,  the  temperature  ascertained,  and  numerous  experiments 
made  as  to  the  digestibility  of  various  kinds  of  food. 

It  was  by  these  careful  and  convincing  experiments  that  the  foundation  of  our 
exact  knowledge  of  the  composition  and  action  of  gastric  juice  was  laid.  The 
modest  book  in  which  Dr.  Beaumont  published  his  results  is  still  counted  among  the 
classics  of  physiology.  The  production  of  artificial  fistulae  in  animals,  a  method  that 
has  since  proved  so  fruitful,  was  first  suggested  by  his  work. 


DIGESTION. 


57 


It  cannot  be  too  strongly  stated  that  food  of  a  simple  char- 
acter, well  cooked  and  neatly  served,  is  more  productive  of 
healthful  living  than  a  great  variety  of  fancy  dishes  which  un- 
duly stimulate  the  digestive  organs,  and  create  a  craving  for 
food  in  excess  of  the  bodily  needs. 

168.  The  Proper  Care  of  the  Teeth.  It  is  our  duty  not 
only  to  take  the  very  best  care  of  our  teeth,  but  to  retain  them 
as  long  as  possible.  Teeth, 
as  we  well  know,  are  prone 
to  decay.  We  may  inherit 
poor  and  soft  teeth:  our  mode 
of  living  may  make  bad  teeth 
worse.  If  an  ounce  of  pre- 
vention is  ever  worth  a  pound 
of  cure,  it  is  in  keeping  the 
teeth  in  good  order.  Bad 
teeth  and  toothless  gums 
mean  imperfect  chewing  of 
the  food  and,  hence,  impaired 
digestion.  To  attain  a  health- 
ful old  age,  the  power  of 
vigorous  mastication  must  be 
preserved. 

One  of  the  most  frequent 
causes  of  decay  of  the  teeth 
is  the  retention  of  fragments 
of  food  between  and  around 
them.  The  warmth  and 
moisture  of  the  mouth  make 
these  matters  decompose 
quickly.  The  acid  thus  generated  attacks  the  enamel  of  the 
teeth,  causing  decay  of  the  dentine.  Decayed  teeth  are  often 
the  cause  of  an  offensive  breath  and  a  foul  stomach. 


FIG.  64.  —  Lymphatics  on  the  Inside 
of  the  Right  Hand. 


158  PRACTICAL    PHYSIOLOGY. 

To  keep  the  teeth  clean  and  wholesome,  they  should  be 
thoroughly  cleansed  at  bedtime  and  in  the  morning  with  a 
soft  brush  and  warm  water.  Castile  soap,  and  some  prepared 
tooth-powder  without  grit,  should  be  used,  and  the  brush  should 
be  applied  on  both  sides  of  the  teeth. 

The  enamel,  once  broken  through,  is  never  renewed.  The 
tooth  decays,  slowly  but  surely  :  hence  we  must  guard  against 
certain  habits  which  injure  the  enamel,  as  picking  the  teeth 
with  pins  and  needles.  We  should  never  crack  nuts,  crush 
hard  candy,  or  bite  off  stout  thread  with  the  teeth.  Stiff 
tooth-brushes,  gritty  and  cheap  tooth-powders,  and  hot  food 
and  drink,  often  injure  the  enamel. 

To  remove  fragments  of  food  which  have  lodged  between 
adjacent  teeth,  a  quill  or  wooden  toothpick  should  be  used. 
Even  better  than  these  is  the  use  of  surgeon's  floss,  or  silk, 
which  when  drawn  between  the  teeth,  effectually  dislodges 
retained  particles.  If  the  teeth  are  not  regularly  cleansed  they 
become  discolored,  and  a  hard  coating  known  as  tartar  accumu- 
lates on  them  and  tends  to  loosen  them.  It  is  said  that  after 
the  age  of  thirty  more  teeth  are  lost  from  this  deposit  than 
from  all  other  causes  combined.  In  fact  decay  and  tartar  are 
the  two  great  agents  that  furnish  work  for  the  dentist.1 

169.  Hints  about  Saving  Teeth.  We  should  exercise  the  greatest 
care  in  saving  the  teeth.  The  last  resort  of  all  is  to  lose  a  tooth  by 
extraction.  The  skilled  dentist  will  save  almost  anything  in  the  shape 
of  a  tooth. 

People  are  often  urged  and  consent  to  have  a  number  of  teeth 
extracted  which,  with  but  little  trouble  and  expense,  might  be  kept 

1  The  teeth  of  children  should  be  often  examined  by  the  dentist,  especially  from 
the  beginning  of  the  second  dentition,  at  about  the  sixth  year,  until  growth  is  com- 
pleted. In  infancy  the  mother  should  make  it  a  part  of  her  daily  care  of  the 
child  to  secure  perfect  cleanliness  of  the  teeth.  The  child  thus  trained  will  not,  when 
old  enough  to  rinse  the  mouth  properly  or  to  use  the  brush,  feel  comfortable  after  a 
meal  until  the  teeth  have  been  cleansed.  The  habit  thus  formed  is  almost  sure  to  be 
continued  through  life. 


DIGESTION.  1 59 

and  do  good  service  for  years.  The  object  is  to  replace  the  teeth 
with  an  artificial  set.  Very  few  plates,  either  partial  or  entire,  are 
worn  with  real  comfort.  They  should  always  be  removed  before 
going  to  sleep,  as  there  is  danger  of  their  being  swallowed. 

The  great  majority  of  drugs  have  no  injurious  effect  upon  the  teeth. 
Some  medicines,  however,  must  be  used  with  great  care.  The  acids 
used  in  the  tincture  of  iron  have  a  great  affinity  for  the  lime  salts  of 
the  teeth.  As  this  form  of  iron  is  often  used,  it  is  not  unusual  to  see 
teeth  very  badly  stained  or  decayed  from  the  effects  of  this  drug. 
The  acid  used  in  the  liquid  preparations  of  quinine  may  destroy  the 
teeth  in  a  comparatively  short  time.  After  taking  such  medicines  the 
mouth  should  be  thoroughly  rinsed  with  a  weak  solution  of  common 
soda,  and  the  teeth  cleansed. 

170.  Alcohol  and  Digestion.  The  influence  of  alcoholic 
drinks  upon  digestion  is  of  the  utmost  importance.  Alcohol 
.is  not,  and  cannot  be  regarded  from  a  physiological  point  of 
view  as  a  true  food.  The  reception  given  to  it  by  the  stomach 
proves  this  very  plainly.  It  is  obviously  an  unwelcome  in- 
truder. It  cannot,  like  proper  foods,  be  transformed  into  any 
element  or  component  of  the  human  body,  but  passes  on,  in- 
nutritious  and  for  the  most  part  unappropriated.  Taken  even 
into  the  mouth,  by  any  person  not  hardened  to  its  use,  its 
effect  is  so  pungent  and  burning  as  at  once  to  demand  its  rejec- 
tion. But  if  allowed  to  pass  into  the  stomach,  that  organ  im- 
mediately rebels  against  its  intrusion,  and  not  unfrequently 
ejects  it  with  indignant  emphasis.  The  burning  sensation  it 
produces  there,  is  only  an  appeal  for  water  to  dilute  it. 

The  stomach  meanwhile,  in  response  to  this  fiery  invitation, 
secretes  from  its  myriad  pores  its  juices  and  watery  fluids, 
to  protect  itself  as  much  as  possible  from  the  invading  liquid. 
It  does  not  digest  alcoholic  drinks ;  we  might  say  it  does  not 
attempt  to,  because  they  are  not  material  suitable  for  digestion, 
and  also  because  no  organ  can  perform  its  normal  work  while 
smarting  under  an  unnatural  irritation. 


l6o  PRACTICAL    PHYSIOLOGY. 

Even  if  the  stomach  does  not  at  once  eject  the  poison,  it 
refuses  to  adopt  it  as  food,  for  it  does  not  pass  along  with  the 
other  food  material,  as  chyme,  into  the  intestines,  but  is  seized 
by  the  absorbents,  borne  into  the  veins,  which  convey  it  to  the 
heart,  whence  the  pulmonary  artery  conveys  it  to  the  lungs, 
where  its  presence  is  announced  in  the  breath.  But  wherever 
alcohol  is  carried  in  the  tissues,  it  is  always  an  irritant,  every 
organ  in  turn  endeavoring  to  rid  itself  of  the  noxious  material. 

171.  Effect  of  Alcoholic  Liquor  upon  the  Stomach.  The 
methods  by  which  intoxicating  drinks  impair  and  often  ruin 
digestion  are  various.  We  know  that  a  piece  of  animal  food, 
as  beef,  if  soaked  in  alcohol  for  a  few  hours,  becomes  hard  and 
tough,  the  fibers  having  been  compacted  together  because  of 
the  abstraction  of  their  moisture  by  the  alcohol,  which  has  a 
marvelous  affinity  for  water.  In  the  same  way  alcohol  hardens 
and  toughens  animal  food  in  the  stomach,  condensing  its  fibers, 
and  rendering  it  indigestible,  thus  preventing-  the  healthful 
nutrition  of  the  body.  So,  if  alcohol  be  added  to  the  clear, 
liquid  white  of  an  egg,  it  is  instantly  coagulated  and  trans- 
formed into  hard  albumen.  As  a  result  of  this  hardening 
action,  animal  food  in  contact  with  alcoholic  liquids  in  the 
stomach  remains  undigested,  and  must  either  be  detained  there 
so  long  as  to  become  a  source  of  gastric  disturbance,  or  else 
be  allowed  to  pass  undigested  through  the  pyloric  gate,  and 
then  may  become  a  cause  of  serious  intestinal  disturbance.1 

1  "  If  the  amount  of  alcohol  be  increased,  or  the  repetition  become  frequent,  some 
part  of  it  undergoes  acid  fermentation  in  the  stomach,  and  acid  eructations  or  vomit- 
ings occur.  With  these  phenomena  are  associated  catarrh  of  the  stomach  and  liver 
with  its  characteristic  symptoms, —  loss  of  appetite,  feeble  digestion,  sallowness, 
mental  depression,  and  headache."  —  JAMES  C.  WILSON,  Professor  in  the  Jefferson 
Medical  College,  Philadelphia. 

"  Man  has  recourse  to  alcohol,  not  for  the  minute  quantity  of  energy  which  may 
be  supplied  by  itself,  but  for  its  powerful  influence  on  the  distribution  of  the  energy 
furnished  by  other  things.  That  influence  is  a  very  complex  one."  —  PROFESSOR 
MICHAEL  FOSTER. 


DIGESTION.  l6l 

This  peculiar  property  of  alcohol,  its  greedy  absorption  of 
water  from  objects  in  contact  with  it,  acts  also  by  absorbing 
liquids  from  the  surface  of  the  stomach  itself,  thus  hardening 
the  delicate  glands,  impairing  their  ability  to  absorb  the  food- 
liquids,  and  so  inducing  gastric  dyspepsia.  This  local  injury 
inflicted  upon  the  stomach  by  all  forms  of  intoxicants,  is  serious 
and  protracted.  This  organ  is,  with  admirable  wisdom,  so  con- 
structed as  to  endure  a  surprising  amount  of  abuse,  but  it  was 
plainly  not  intended  to  thrive  on  alcoholic  liquids.  The  appli- 
cation of  fiery  drinks  to  its  tender  surface  produces  at  first 
a  marked  congestion  of  its  blood-vessels,  changing  the  natural 
pink  color,  as  in  the  mouth,  to  a  bright  or  deep  red. 

If  the  irritation  be  not  repeated,  the  lining  membrane  soon 
recovers  its  natural  appearance.  But  if  repeated  and  con- 
tinued, the  congestion  becomes  more  intense,  the  red  color 
deeper  and  darker  ;  the  entire  surface  is  the  subject  of  chronic 
inflammation,  its  walls  are  thickened,  and  sometimes  ulcerated. 
In  this  deplorable  state,  the  organ  is  quite  unable  to  perform 
its  normal  work  of  digestion.1 

172.  Alcohol  and  the  Gastric  Juice.  But  still  another 
destructive  influence  upon  digestion  appears  in  the  singular 
fact  that  alcohol  diminishes  the  power  of  the  gastric  juice  to 
do  its  proper  work.  Alcohol  coagulates  the  pepsin,  which  is 
the  dissolving  element  in  this  important  gastric  fluid.  A  very 
simple  experiment  will  prove  this.  Obtain  a  small  quantity  of 
gastric  juice  from  the  fresh  stomach  of  a  calf  or  pig,  by  gently 
pressing  it  in  a  very  little  water.  Pour  the  milky  juice  into  a 
clear  glass  vessel,  add  a  little  alcohol,  and  a  white  deposit  will 
presently  settle  to  the  bottom.  This  deposit  contains  the  pep- 

1  "  When  constantly  irritated  by  the  direct  action  of  alcoholic  drinks,  the  stomach 
gradually  undergoes  lasting  structural  changes.  Its  vessels  remain  dilated  and  con- 
gested, its  connective  tissue  becomes  excessive,  its  power  of  secreting  gastric  juice 
diminishes,  and  its  mucous  secretions  abnormally  abundant."  —  H.  NEWELL  MAR- 
TIN, late  Professor  of  Physiology  in  Johns  Hopkins  University. 


1 62  PRACTICAL    PHYSIOLOGY. 

sin  of  the  gastric  juice,  the  potent  element  by  which  it  does  its 
special  work  of  digestion.  The  ill  effect  of  alcohol  upon  it  is 
one  of  the  prime  factors  in  the  long  series  of  evil  results  from 
the  use  of  intoxicants. 

173.  The  Final  Results  upon  Digestion.  We  have  thus 
explained  three  different  methods  by  which  alcoholic  drinks 
exercise  a  terrible  power  for  harm ;  they  act  upon  the  food  so 
as  to  render  it  less  digestible;  they  injure  the  stomach  so  as 
seriously  to  impair  its  power  of  digestion;  and  they  deprive 
the  gastric  juice  of  the  one  principal  ingredient  essential  to 
its  usefulness. 

Alcoholic  drinks  forced  upon  the  stomach  are  a  foreign 
substance ;  the  stomach  treats  them  as  such,  and  refuses  to  go 
on  with  the  process  of  digestion  till  it  first  gets  rid  of  the  poi- 
son. This  irritating  presence  and  delay  weaken  the  stomach, 
so  that  when  proper  food  follows,  the  enfeebled  organ  is  ill 
prepared  for  its  work.  After  intoxication,  there  occurs  an 
obvious  reaction  of  the  stomach  and  digestive  organs,  against 
the  violent  and  unnatural  disturbance.  The  appetite  is  extin- 
guished or  depraved,  and  intense  headache  racks  the  frame; 
the  whole  system  is  prostrated,  as  from  a  partial  paralysis  (all 
these  results  being  the  voice  of  Nature's  sharp  warning  of  this 

"  Chemical  experiments  have  demonstrated  that  the  action  of  alcohol  on  the 
digestive  fluids  is  to  destroy  its  active  principle,  the  pepsin,  thus  confirming  the 
observations  of  physiologists  that  its  use  gives  rise  to  the  most  serious  disorders  of 
the  stomach  and  the  most  malignant  aberrations  of  the  entire  economy."  —  PRO- 
FESSOR E.  C.  YOUMANS,  author  of  standard  scientific  works. 

"  The  structural  changes  induced  by  the  habitual  use  of  alcohol  and  the  action  of 
this  agent  on  the  pepsin,  seriously  impair  the  digestive  power.  Hence  it  is,  that 
those  who  are  habitual  consumers  of  alcoholic  fluids  suffer  from  disorders  of  digestion." 
—  ROBERT  BARTHOLOW,  recently  Professor  of  Materia  Medica  in  the  University  of 
Pennsylvania. 

"Alcohol  in  any  appreciable  quantity  diminishes  the  solvent  power  of  the  gastric 
fluid  so  as  to  interfere  with  the  process  of  digestion  instead  of  aiding  it."  —  PRO- 
FESSOR W.  B.  CARPENTER,  the  eminent  English  physiologist. 


DIGESTION.  163 

great  wrong),  and  a  rest  of  some  days  is  needed  before  the 
system  fully  recovers  from  the  injury  inflicted. 

It  is  altogether  an  error  to  suppose  the  use  of  intoxicants  is 
necessary  or  even  desirable  to  promote  appetite  or  digestion. 
In  health,  good  food  and  a  stomach  undisturbed  by  artificial 
interference  furnish  all  the  conditions  required.  More  than 
these  is  harmful.  If  it  may  sometimes  seem  as  if  alcoholic 
drinks  arouse  the  appetite  and  invigorate  digestion,  we -must  not 
shut  our  eyes  to  the  fact  that  this  is  only  a  seeming,  and  that 
their  continued  use  will  inevitably  ruin  both.  In  brief,  there 
is  no  more  sure  foe  to  good  appetite  and  normal  digestion 
than  the  habitual  use  of  alcoholic  liquors. 

174.  Effect  of  Alcoholic  Drinks  upon  the  Liver.  It  is  to 
be  noted  that  the  circulation  of  the  liver  is  peculiar  ;  that  the 
capillaries  of  the  hepatic  artery  unite  in  the  lobule  with  those 
of  the  portal  vein,  and  thus  the  blood  from  both  sources  is 
combined  ;  and  that  the  portal  vein  brings  to  the  liver  the  blood 
from  the  stomach,  the  intestines,  and  the  spleen.  From  the 
fact  that  alcohol  absorbed  from  the  stomach  enters  the  portal 
vein,  and  is  borne  directly  to  the  liver,  we  would  expect  to 
find  this  organ  suffering  the  full  effects  of  its  presence.  And 
all  the  more  would  this  be  true,  because  we  have  just  learned 
that  the  liver  acts  as  a  sort  of  filter  to  strain  from  the  blood  its 
impurities.  So  the  liver  is  especially  liable  to  diseases  pro- 
duced by  alcoholics.  Post  mortems  of  those  who  have  died 
while  intoxicated  show  a  larger  amount  of  alcohol  in  the  liver 
than  in  any  other  organ.  Next  to  the  stomach  the  liver  is  an 
early  and  late  sufferer,  and  this  is  especially  the  case  with  hard 
drinkers,  and  even  more  moderate  drinkers  in  hot  climates. 
Yellow  fever  occurring  in  inebriates  is  always  fatal. 

The  effects  produced  in  the  liver  are  not  so  much  functional 
as  organic;  that  is,  not  merely  a  disturbed  mode  of  action,  but 
a  destruction  of  the  fabric  of  the  organ  itself.  From  the  use 


164  PRACTICAL    PHYSIOLOGY. 

of  intoxicants,  the  liver  becomes  at  first  irritated,  then  inflamed, 
and  finally  seriously  diseased.  The  fine  bands,  or  septa,  which 
serve  as  partitions  between  the  hepatic  lobules,  and  so  maintain 
the  form  and  consistency  of  the  organ,  are  the  special  subjects  of 
the  inflammation.  Though  the  liver  is  at  first  enlarged,  it  soon 
becomes  contracted;  the  secreting  cells  are  compressed,  and 
are  quite  unable  to  perform  their  proper  work,  which  indeed  is 
a  very  important  one  in  the  round  of  the  digestion  of  food  and 
the  purification  of  the  blood.  This  contraction  of  the  septa 
in  time  gives  the  whole  organ  an  irregularly  puckered  appear- 
ance, called  from  this  fact  a  hob-nail  liver  or,  popularly,  gin 
liver.  The  yellowish  discoloration,  usually  from  retained  or 
perverted  bile,  gives  the  disease  the  medical  name  of  cirrhosis.1 
It  is  usually  accompanied  with  dropsy  in  the  lower  extremities, 
caused  by  obstruction  to  the  return  of  the  circulation  from  the 
parts  below  the  liver.  This,  disease  is  always  fatal. 

175.  Fatty  Degeneration  Due  to  Alcohol.  Another  form 
of  destructive  disease  often  occurs.  There  is  an  increase  of 
fat  globules  deposited  in  the  liver,  causing  notable  enlarge- 
ment and  destroying  its  function.  This  is  called  fatty  degener- 
ation, and  is  not  limited  to  the  liver,  but  other  organs  are 
likely  to  be  similarly  affected.  In  truth,  this  deposition  of  fat 
is  a  most  significant  occurrence,  as  it  means  actual  destruction 
of  the  liver  tissues,  —  nothing  less  than  progressive  death  of  the 
organ.  This  condition  always  leads  to  a  fatal  issue.  Still 
other  forms  of  alcoholic  disease  of  the  liver  are  produced,  one 
being  the  excessive  formation  of  sugar,  constituting  what  is 
known  as  a  form  of  diabetes. 

1 "  Cirrhosis  of  the  liver  is  notoriously  frequent  among  drunkards,  and  is  in  fact 
almost,  though  not  absolutely,  confined  to  them."  —  ROBERT  T.  EDES,  formerly 
Professor  of  Materia  Medica  in  Harvard  Medical  College. 

"  Alcohol  acts  on  the  liver  by  producing  enlargement  of  that  organ,  and  a  fatty 
deposit,  or  'hob-nailed'  liver  mentioned  by  the  English  writers." — PROFESSOR 
W.  B.  CARPENTER. 


DIGESTION.  165 

176.  Effect  of  Tobacco  on  Digestion.  The  noxious  in- 
fluence of  tobacco  upon  the  process  of  digestion  is  nearly 
parallel  to  the  effects  of  alcohol,  which  it  resembles  in  its  irri- 
tant and  narcotic  character.  Locally,  it  stimulates  the  secre- 
tion of  saliva  to  an  unnatural  extent,  and  this  excess  of  secretion 
diminishes  the  amount  available  for  normal  digestion. 

Tobacco  also  poisons  the  saliva  furnished  for  the  digestion 
of  food,  and  thus  at  the  very  outset  impairs,  in  both  of  these 
particulars,  the  general  digestion,  and  especially  the  digestion 
of  the  starchy  portions  of  the  food.  For  this  reason  the 
amount  of  food  taken,  fails  to  nourish  as  it  should,  and  either 
more  food  must  be  taken,  or  the  body  becomes  gradually 
impoverished. 

The  poisonous  nicotine,  the  active  element  of  tobacco,  exerts 
a  destructive  influence  upon  the  stomach  digestion,  enfeebling 
the  vigor  of  the  muscular  walls  of  that  organ.  These  effects 
combined  produce  dyspepsia,  with  its  weary  train  of  bane- 
ful results. 

The  tobacco  tongue  never  presents  the  natural,  clear,  pink 
color,  but  rather  a  dirty  yellow,  and  is  usually  heavily  coated, 
showing  a  disordered  stomach  and  impaired  digestion.  Then, 
too,  there  is  dryness  of  the  mouth,  an  unnatural  thirst  that 
demands  drink.  But  pure  water  is  stale  and  flat  to  such  a 
mouth:  something  more  emphatic  is  needed.  Thus  comes  the 
unnatural  craving  for  alcoholic  liquors,  and  thus  are  taken  the 
first  steps  on  the  downward  grade. 

"  There  is  no  doubt  that  tobacco  predisposes  to  neuralgia,  vertigo,  indigestion, 
and  other  affections  of  the  nervous,  circulatory  and  digestive  organs."  —  W.  H. 
HAMMOND,  the  eminent  surgeon  of  New  York  city  and  formerly  Surgeon  General, 
U.  S.  A. 

Drs.  Seaver  of  Yale  University  and  Hitchcock  of  Amherst  College,  instructors  of 
physical  education  in  these  two  colleges,  have  clearly  demonstrated  by  personal  ex- 
amination and  recorded  statistics  that  the  use  of  tobacco  among  college  students 
checks  growth  in  weight,  height,  chest-girth,  and,  most  of  all,  in  lung  capacity. 


1 66  PRACTICAL    PHYSIOLOGY. 


ADDITIONAL   EXPERIMENTS. 

Experiment  66.  Test  a  portion  of  C  (Experiment  57)  with  solution  of 
iodine ;  no  blue  color  is  obtained,  as  all  the  starch  has  disappeared,  having 
been  converted  into  a  reducing  sugar,  or  maltose. 

Experiment  67.  Make  a  thick  starch  paste ;  place  some  in  test  tubes, 
labeled  A  and  B.  Keep  A  for  comparison,  and  to  B  add  saliva,  and  ex- 
pose both  to  about  104°  F.  A  is  unaffected,  while  B  soon  becomes  fluid 
—  within  two  minutes  —  and  loses  its  opalescence;  this  liquefaction  is  a 
process  quite  antecedent  to  the  saccharifying  process  which  follows. 

Experiment  68.  To  show  the  action  of  gastric  juice  on  milk.  Mix 
two  teaspoonfuls  of  fresh  milk  in  a  test  tube  with  a  few  drops  of  neutral 
artificial  gastric  juice;1  keep  at  about  100°  F.  In  a  short  time  the  milk 
curdles,  so  that  the  tube  can  be  inverted  without  the  curd  falling  out.  By 
and  by  whey  is  squeezed  out  of  the  clot.  The  curdling  of  milk  by  the 
rennet  ferment  present  in  the  gastric  juice,  is  quite  different  from  that  pro- 
duced by  the  "  souring  of  milk,"  or  by  the  precipitation  of  caseinogen  by 
acids.  Here  the  casein  (carrying  with  it  most  of  the  fats)  is  precipitated 
in  a  neutral  fluid. 

Experiment  69.  To  the  test  tube  in  the  preceding  experiment,  add 
two  teaspoonfuls  of  dilute  hydrochloric  acid,  and  keep  at  100°  F.  for  two 
hours.  The  pepsin  in  the  presence  of  the  acid  digests  the  casein,  gradually 
dissolving  it,  forming  a  straw-colored  fluid  containing  peptones.  The  pep- 
tonized  milk  has  a  peculiar  odor  and  bitter  taste. 

Experiment  70.  To  show  the  action  of  rennet  on  milk.  Place  milk  in 
a  test  tube,  add  a  drop  or  two  of  commercial  rennet,  and  place  the  tube  in 

i  Preparation  of  Artificial  Gastric  Juice,  (a)  Take  part  of  the  cardiac  end  of 
the  pig's  stomach,  which  has  been  previously  opened  and  washed  rapidly  in  cold 
water,  and  spread  it,  mucous  surface  upwards,  on  the  convex  surface  of  an  inverted 
capsule.  Scrape  the  mucous  surface  firmly  with  the  back  of  a  knife  blade,  and  rub 
up  the  scrapings  in  a  mortar  with  fine  sand.  Add  water,  and  rub  up  the  whole  vigor- 
ously for  some  time,  and  filter.  The  filtrate  is  an  artificial  gastric  juice. 

(b)  From  the  cardiac  end  of  a  pig's  stomach  detach  the  mucous  membrane  in 
shreds,  dry  them  between  folds  of  blotting-paper,  place  them  in  a  bottle,  and  cover 
them  with  strong  glycerine  for  several  days.  The  glycerine  dissolves  the  pepsin,  and 
on  filtering,  a  glycerine  extract  with  high  digestive  properties  is  obtained. 

These  artificial  juices,  when  added  to  hydrochloric  acid  of  the  proper  strength, 
have  high  digestive  powers. 

Instead  of  (a)  or  (£)  use  the  artificial  pepsin  prepared  for  the  market  by  the 
wholesale  manufacturers  of  such  goods. 


DIGESTION.  167 

a  water-bath  at  about  100°  F.  The  milk  becomes  solid  in  a  few  minutes, 
forming  a  curd,  and  by  and  by  the  curd  of  casein  contracts,  and  presses 
out  a  fluid,  —  the  whey. 

Experiment  71.  Repeat  the  experiment,  but  previously  boil  the  rennet. 
No  such  result  is  obtained  as  in  the  preceding  experiment,  because  the 
rennet  ferment  is  destroyed  by  heat. 

Experiment  72.  To  show  the  effect  of  the  pancreatic  ferment  (tryp- 
siri)  upon  albuminous  matter.  Half  fill  three  test  tubes,  A,  B,  C,  with  one- 
per-cent  solution  of  sodium  carbonate,  and  add  5  drops  of  liquor  pancrea- 
ticus,  or  a  few  grains  of  Fairchild's  extract  of  pancreas,  in  each.  Boil  B, 
and  make  C  acid  with  dilute  hydrochloric  acid.  Place  in  each  tube  an 
equal  amount  of  well-washed  fibrin,  plug  the  tubes  with  absorbent  cotton, 
and  place  all  in  a  water-bath  at  about  100°  F. 

Experiment  73.  Examine  from  time  to  time  the  three  test  tubes  in  the 
preceding  experiment.  At  the  end  of  one,  two,  or  three  hours,  there  is 
no  change  in  B  and  C,  while  in  A  the  fibrin  is  gradually  being  eroded,  and 
finally  disappears ;  but  it  does  not  swell  up,  and  the  solution  at  the  same 
time  becomes  slightly  turbid.  After  three  hours,  still  no  change  is  observ- 
able in  B  and  C. 

Experiment  74.  Filter  A,  and  carefully  neutralize  the  filtrate  with  very 
dilute  hydrochloric  or  acetic  acid,  equal  to  a  precipitate  of  alkali-albumen. 
Filter  off  the  precipitate,  and  on  testing  the  filtrate,  peptones  are  found. 
The  intermediate  bodies,  the  albumoses,  are  not  nearly  so  readily  obtained 
from  pancreatic  as  from  gastric  digests. 

Experiment  75.  Filter  B  and  C,  and  carefully  neutralize  the  filtrates. 
They  give  no  precipitate.  No  peptones  are  found. 

Experiment  76.  To  show  the  action  of  pancreatic  juice  upon  the  al- 
buminous ingredients  (casein)  of  milk.  Into  a  four-ounce  bottle  put  two 
tablespoonf  uls  of  cold  water ;  add  one  grain  of  Fairchild's  extract  of  pan- 
creas, and  as  much  baking  soda  as  can  be  taken  up  on  the  point  of  a  pen- 
knife. Shake  well,  and  add  four  tablespoonf  uls  of  cold,  fresh  milk.  Shake 
again. 

Now  set  the  bottle  into  a  basin  of  hot  water  (as  hot  as  one  can  bear  the 
hand  in),  and  let  it  stand  for  about  forty-five  minutes.  While  the  milk  is 
digesting,  take  a  small  quantity  of  milk  in  a  goblet,  and  stir  in  ten  drops 
or  more  of  vinegar.  A  thick  curd  of  casein  will  be  seen. 

Upon  applying  the  same  test  to  the  digested  milk,  no  curd  will  be  made. 
This  is  because  the  pancreatic  ferment  (trypsin)  has  digested  the  casein 
into  "  peptone,"  which  does  not  curdle.  This  digested  milk  is  therefore 
called  "  peptonized  milk." 


1 68  PRACTICAL    PHYSIOLOGY. 

Experiment  77.  To  show  the  action  of  bile.  Obtain  from  the  butcher 
some  ox  bile.  Note  its  bitter  taste,  peculiar  odor,  and  greenish  color.  It 
is  alkaline  or  neutral  to  litmus  paper.  Pour  it  from  one  vessel  to  another, 
and  note  that  strings  of  mucin  (from  the  lining  membrane  of  the  gall 
bladder)  connect  one  vessel  with  the  other.  It  is  best  to  precipitate  the 
mucin  by  acetic  acid  before  making  experiments;  and  to  dilute  the  clear 
liquid  with  a  little  distilled  water. 

Experiment  78.  Test  for  bile  pigments.  Place  a  few  drops  of  bile  on 
a  white  porcelain  slab.  With  a  glass  rod  place  a  drop  or  two  of  strong 
nitric  acid  containing  nitrous  acid  near  the  drop  of  bile ;  bring  the  acid 
and  bile  into  contact.  Notice  the  succession  of  colors,  beginning  with 
green  and  passing  into  blue,  red,  and  yellow. 

Experiment  79.  To  show  the  action  of  bile  on  fats.  Mix  three  tea- 
spoonfuls  of  bile  with  one-half  a  teaspoonful  of  almond  oil,  to  which  some 
oleic  acid  is  added.  Shake  well,  and  keep  the  tube  in  a  water-bath  at  about 
1 00°  F.  A  very  good  emulsion  is  obtained. 

Experiment  80.  To  show  that  bile  favors  filtration  and  the  absorption 
of  fats.  Place  two  small  funnels  of  exactly  the  same  size  in  a  filter  stand, 
and  under  each  a  beaker.  Into  each  funnel  put  a  filter  paper;  moisten 
the  one  with  water  (A)  and  the  other  with  bile  (B).  Pour  into  each  an 
equal  volume  of  almond  oil ;  cover  with  a  slip  of  glass  to  prevent  evapora- 
tion. Set  aside  for  twelve  hours,  and  note  that  the  oil  passes  through  B, 
but  scarcely  any  through  A.  The  oil  filters  much  more  readily  through 
the  one  moistened  with  bile,  than  through  the  one  moistened  with  water. 


EXPERIMENTS  WITH  THE  FATS. 

Experiment  81.  Use  olive  oil  or  lard.  Show  by  experiment  that  they 
are  soluble  in  ether,  chloroform  and  hot  water,  but  insoluble  in  water  alone. 

Experiment  82.  Dissolve  a  few  drops  of  oil  or  fat  in  a  teaspoonful  of 
ether.  Let  a  drop  of  the  solution  fall  on  a  piece  of  tissue  or  rice  paper. 
Note  the  greasy  stain,  which  does  not  disappear  with  the  heat. 

Experiment  83.  Pour  a  little  cod-liver  oil  into  a  test  tube;  add  a  few 
drops  of  a  dilute  solution  of  sodium  carbonate.  The  whole  mass  becomes 
white,  making  an  emulsion. 

Experiment  84.  Shake  up  olive  oil  with  a  solution  of  albumen  in  a 
test  tube.  Note  that  an  emulsion  is  formed. 


CHAPTER   VII. 
THE    BLOOD    AND    ITS    CIRCULATION. 

177.  The  Circulation.  All  the  tissues  of  the  body  are 
traversed  by  exceedingly  minute  tubes  called  capillaries,  which 
receive  the  blood  from  the  arteries,  and  convey  it  to  the  veins. 
These  capillaries  form  a  great  system  of  networks,  the  meshes 
of  which  are  filled  with  the  elements  of  the  various  tissues. 
That  is,  the  capillaries  are  closed  vessels,  and  the  tissues  lie 
outside  of  them,  as  asbestos  packing  may  be  used  to  en- 
velop hot-water  pipes.  The  space  between  the  walls  of  the 
capillaries  and  the  cells  of  the  tissues  is  filled  with  lymph. 
As  the  blood  flows  along  the  capillaries,  certain  parts  of  the 
plasma  of  the  blood  filter  through  their  walls  into  the  lymph, 
and  certain  parts  of  the  lymph  filter  through  the  cell  walls  of 
the  tissues  and  mingle  with  the  blood  current.  The  lymph 
thus  acts  as  a  medium  of  exchange,  in  which  a  transfer  of 
material  takes  place  between  the  blood  in  the  capillaries  and  the 
lymph  around  them.  A  similar  exchange  of  material  is  constantly 
going  on  between  the  lymph  and  the  tissues  themselves. 

This,  then,  we  must  remember,  —  that  in  every  tissue,  so 
long  as  the  blood  flows,  and  life  lasts,  this  exchange  takes  place 
between  the  blood  within  the  capillaries  and  the  tissues  without. 

The  stream  of  blood  to  the  tissues  carries  to  them  the 
material,  including  the  all-important  oxygen,  with  which  they 
build  themselves  up  and  do  their  work.  The  stream  from 
the  tissues  carries  into  the  blood  the  products  of  certain  chem- 
ical changes  which  have  taken  place  in  these  tissues.  These 
products  may  represent  simple  waste  matter  to  be  cast  out  or 
material  which  may  be  of  use  to  some  other  tissue. 


I/O  PRACTICAL    PHYSIOLOGY. 

In  brief,  the  tissues  by  the  help  of  the  lymph  live  on  the 
blood.  Just  as  our  bodies,  as  a  whole,  live  on  the  things 
around  us,  the  food  and  the  air,  so  do  the  bodily  tissues  live 
on  the  blood  which  bathes  them  in  an  unceasing  current,  and 
which  is  their  immediate  air  and  food. 

178.  Physical  Properties  of  Blood.  The  blood  has  been 
called  the  life  of  the  body  from  the  fact  that  upon  it  depends 
our  bodily  existence.  The  blood  is  so  essentially  the  nutrient 

element  that  it  is  called  some- 
times very  aptly  "  liquid  flesh." 
It  is  a  red,  warm,  heavy,  alkaline 
fluid,  slightly  salt  in  taste,  and 
has  a  somewhat  fetid  odor.     Its 
color  varies  from  bright  red  in 
the  arteries   and  when   exposed 
FIG.  65.  — Blood  Corpuscles  of  Van-  to  the  air,  to  various  tints  from 
ous  Animals.     (Magnified  to  the  dark  purple  to  red  in  the  veins. 

The  color  of  the  blood  is  due  to 
A'^T^f?4^^  the  colo™g  constituent  of  the  red 

of  acetic  acid,  showing  the  central  nu-  COrpUSCleS,  JlCBmOglobin,  which  is 
cleus;  E  bird;  F,  camel;  G,  fish;  H,  feri  hter  Qr  darker  ^  ft  contains 
crab  or  other  invertebrate  animal. 

more  or  less  oxygen. 

The  temperature  of  the  blood  varies  slightly  in  different 
parts  of  the  circulation.  Its  average  heat  near  the  surface  is 
in  health  about  the  same,  viz.  98^-°  F.  Blood  is  alkaline,  but 
outside  of  the  body  it  soon  becomes  neutral,  then  acid.  The 
chloride  of  sodium,  or  common  salt,  which  the  blood  contains, 
gives  it  a  salty  taste.  In  a  hemorrhage  from  the  lungs,  the 
sufferer  is  quick  to  notice  in  the  mouth  the  warm  and  saltish 
taste.  The  total  amount  of  the  blood  in  the  body  was  formerly 
greatly  overestimated.  It  is  about  T^  of  the  total  weight  of 
the  body,  and  in  a  person  weighing  156  pounds  would  amount 
to  about  12  pounds. 


THE    BLOOD    AND    ITS    CIRCULATION.  I /I 

179.  Blood  Corpuscles.     If  we  put  a  drop  of  blood  upon  a 
glass  slide,  and  place  upon  it  a  cover  of  thin  glass,  we  can 
flatten  it  out  until  the  color  almost  disappears.     If  we  examine 
this  thin  film  with  a  microscope,  we  see  that  the  blood  is  not 
altogether  fluid.     We  find  that  the  liquid  part,  or  plasma,  is  of 
a  light  straw  color,  and  has  floating  in  it  a  multitude  of  very 
minute  bodies,  called  corpuscles.     These  are  of  two  kinds,  the 
red  and  the  colorless.     The  former  are  much  more  numerous, 
and  have  been   compared   somewhat   fancifully  to  countless 
myriads  of  tiny  fishes  in  a  swiftly  flowing  stream. 

180.  Red  Corpuscles.      The  red  corpuscles  are  circular 
disks  about  ^^^  of  an  inch  in  diameter,  and  double  concave 
in  shape.     They  tend  to  adhere  in  long  rolls  like  piles  of  coins. 
They  are  soft,  flexible,  and  elastic,  readily  squeezing  through 
openings  and  passages  narrower  than  their  pwn  diameter,  then 
at  once  resuming  their  own  shape. 

The  red  corpuscles  are  so  very  small,  that  rather  more  than 
ten  millions  of  them  will  lie  on  a  surface  one  inch  square. 
Their  number  is  so  enormous  that,  if  all  the  red  corpuscles  in 
a  healthy  person  could  be  arranged  in  a  continuous  line,  it  is 
estimated  that  they  would  reach  four  times  around  the  earth ! 
The  principal  constituent  of  these  corpuscles,  next  to  water, 
and  that  which  gives  them  color  is  hcemoglobin,  a  compound 
containing  iron.  As  all  the  tissues  are  constantly  absorbing 
oxygen,  and  giving  off  carbon  dioxid,  a  very  important  office 
of  the  red  corpuscles  is  to  carry  oxygen  to  all  parts  of  the  body. 

181.  Colorless  Corpuscles.     The  colorless  corpuscles  are 

larger  than  the  red,  their  average  diameter  being  about  ^W 
of  an  inch.  While  the  red  corpuscles  are  regular  in  shape, 
and  float  about,  and  tumble  freely  over  one  another,  the  color- 
less are  of  irregular  shape,  and  stick  close  to  the  glass  slide 
on  which  they  are  placed.  Again,  while  the  red  corpuscles  are 
changed  only  by  some  influence  from  without,  as  pressure  and 


172 


PRACTICAL    PHYSIOLOGY. 


the  like,  the  colorless  corpuscles  spontaneously  undergo  active 
and  very  curious  changes  of  form,  resembling  those  of  the 
amoeba,  a  very  minute  organism  found  in  stagnant  water 
(Fig.  2). 

The  number  of  both  red  and  colorless  corpuscles  varies  a 
great  deal  from  time  to  time.  For  instance,  the  number  of  the 
latter  increases  after  meals,  and  quickly  diminishes.  There  is 
reason  to  think  both  kinds  of  corpuscles  are 
continually  being  destroyed,  their  place  being 
supplied  by  new  ones.  While  the  action  of  the 
colorless  corpuscles  is  important  to  the  lymph 
and  the  chyle,  and  in  the  coagulation  of  the 
blood,  their  real  function  has  not  been  ascer- 
tained. 


Experiment  85.  To  show  the  blood  corpuscles.  A 
moderately  powerful  microscope  is  necessary  to  examine 
blood  corpuscles.  Let  a  small  drop  of  blood  (easily 
obtained  by  pricking  the  finger  with  a  needle)  be  placed 
upon  a  clean  slip  of  glass,  and  covered  with  thin  glass, 
such  as  is  ordinarily  used  for  microscopic  purposes. 

The  blood  is  thus  spread  out  into  a  film,  and  may  be 
readily  examined.  At  first  the  red  corpuscles  will  be 
seen  as  pale,  disk-like  bodies  floating  in  the  clear  fluid. 
Soon  they  will  be  observed  to  stick  to  each  other  by 
their  flattened  faces,  so  as  to  form  rows.  The  colorless 
corpuscles  are  to  be  seen  among  the  red  ones,  but  are 
much  less  numerous. 


FIG.    66.  —  Blood 
Corpuscles  of  Man. 

A,  red  corpuscles ; 
B,  the  same  seen 
edgeways;  C,  the 
same  arranged  in 
rows  ;  D ,  white  cor- 
puscles with  nuclei. 


182.  The  Coagulation  of  the  Blood.  Blood  when  shed 
from  the  living  body  is  as  fluid  as  water.  But  it  soon  becomes 
viscid,  and  flows  less  readily  from  one  vessel  to  another.  Soon 
the  whole  mass  becomes  a  nearly  solid  jelly  called  a  clot. 
The  vessel  containing  it  even  can  be  turned  upside  down,  with- 
out a  drop  of  blood  being  spilled.  If  carefully  shaken  out,  the 
mass  will  form  a  complete  mould  of  the  vessel. 


THE    BLOOD    AND    ITS    CIRCULATION. 


At  first  the  clot  includes  the  whole  mass  of  blood,  takes  the 
shape  of  the  vessel  in  which  it  is  contained,  and  is  of  a  uniform 
color.  But  in  a  short  time  a  pale  yellowish  fluid  begins  to 
ooze  out,  and  to  collect  on  the  surface.  The  clot  gradually 
shrinks,  until  at  the  end  of  a  few  hours  it  is  much  firmer,  and 
floats  in  the  yellowish  fluid.  The  white  corpuscles  become 
entangled  in  the  upper  portion  of  clot,  giving  it  a  pale  yellow 
look  on  the  top,  known  as  the  buffy  coat.  As  the  clot  is 
attached  to  the  sides  of  the  vessel,  the 
shrinkage  is  more  pronounced  toward  the  & 
center,  and  thus  the  surface  of  the  clot  is 
hollowed  or  cupped,  as  it  is  called.  This 
remarkable  process  is  known  as  coagula- 
tion, or  the  clotting  of  blood ;  and  the 
liquid  which  separates  from  the  clot  is  FlG.  6;>  _  Diagram  of 
called  serum.  The  serum  is  almost  en-  Clot  with  Buffy  Coat, 
tirely  free  from  corpuscles,  these  being  A,  serum ;  B,  cupped  upper 
entangled  in  the  fibrin. 

This  clotting  of  the  blood  is  due  to  the 
formation  in  the  blood,  after  it  is  with- 
drawn from  the  living  body,  of  a  sub- 
stance called  fibrin.1  It  is  made  up  of  a  network  of  fine  white 
threads,  running  in  every  direction  through  the  plasma,  and  is 
a  proteid  substance.  The  coagulation  of  the  blood  may  be 
retarded,  and  even  prevented,  by  a  temperature  below  40°  F., 
or  a  temperature  above  120°  F.  The  addition  of  common  salt 
also  prevents  coagulation.  The  clotting  of  the  blood  may  be 
hastened  by  free  access  to  air,  by  contact  with  roughened  sur- 
faces, or  by  keeping  it  at  perfect  rest. 


surface  of  dot  ;  c,  white 

corpuscles  in  upper  layer 

of  clot;    D,  lower  por- 
tion  °f  clot  with  red  cor- 

puscles. 


1  The  cause  of  the  clotting  of  blood  is  not  yet  fully  understood.  Although  the 
process  has  been  thoroughly  investigated  we  have  not  yet  a  satisfactory  explanation 
why  the  circulating  blood  does  not  clot  in  healthy  blood-vessels.  The  ablest  physiol- 
ogists of  our  day  do  not,  as  formerly,  regard  the  process  as  a  so-called  vital,  but  a 
purely  chemical  one. 


PRACTICAL    PHYSIOLOGY. 

This  power  of  coagulation  is  of  the  most  vital  importance. 
But  for  this,  a  very  small  cut  might  cause  bleeding  sufficient 
to  empty  the  blood-vessels,  and  death  would  speedily  follow. 
In  slight  cuts,  Nature  plugs  up  the  wound  with  clots  of  blood, 
and  thus  prevents  excessive  bleeding.  The  unfavorable  effects 
of  the  want  of  clotting  are  illustrated  in  some  persons  in  whom 
bleeding  from  even  the  slightest  wounds  continues  till  life  is  in 
danger.  Such  persons  are  called  "bleeders,"  and  surgeons 
hesitate  to  perform  on  them  any  operation,  however  trivial,  even 
the  extraction  of  a  tooth  being  often  followed  by  an  alarming 
loss  of  blood. 

Experiment  86.  A  few  drops  of  fresh  blood  may  be  easily  obtained  to 
illustrate  important  points  in  the  physiology  of  blood,  by  tying  a  string 
tight  around  the  finger,  and  piercing  it  with  a  clean  needle.  The  blood 
runs  freely,  is  red  and  opaque.  Put  two  or  three  drops  of  fresh  blood  on 
a  sheet  of  white  paper,  and  observe  that  it  looks  yellowish. 

Experiment  87.  Put  two  or  three  drops  of  fresh  blood  on  a  white 
individual  butter  plate  inverted  in  a  saucer  of  water.  Cover  it  with  an 
inverted  goblet.  Take  off  the  cover  in  five  minutes,  and  the  drop  has  set 
into  a  jelly-like  mass.  Take  it  off  in  half  an  hour,  and  a  little  clot  will  be 
seen  in  the  watery  serum. 

Experiment  88.  To  show  the  blood-clot.  Carry  to  the  slaughter  house 
a  clean,  six  or  eight  ounce,  wide-mouthed  bottle.  Fill  it  with  fresh  blood. 
Carry  it  home  with  great  care,  and  let  it  stand  over  night.  The  next  day 
the  clot  will  be  seen  floating  in  the  nearly  colorless  serum. 

Experiment  89.  Obtain  a  pint  of  fresh  blood;  put  it  into  a  bowl,  and 
whip  it  briskly  for  five  minutes,  with  a  bunch  of  dry  twigs.  Fine  white 
threads  of  fibrin  collect  on  the  twigs,  the  blood  remaining  fluid.  This  is 
"  whipped  "  or  defibrinated  blood,  which  has  lost  the  power  of  coagulating 
spontaneously. 

183.  General  Plan  of  Circulation.  All  the  tissues  of  the 
body  depend  upon  the  blood  for  their  nourishment.  It  is 
evident  then  that  this  vital  fluid  must  be  continually  renewed, 
else  it  would  speedily  lose  all  of  its  life-giving  material.  Some 


THE    BLOOD    AND    ITS    CIRCULATION. 

provision,  then,  is  necessary  not  only  to  have  the  blood 
renewed  in  quantity  and  quality,  but  also  to  enable  it  to  carry 
away  impurities. 

So  we  must  have  an  apparatus  of  circulation.  We  need 
first  a  central  pump  from  which  branch  off  large  pipes,  which 
divide  into  smaller  and  smaller  branches  until  they  reach 
the  remotest  tissues. 
Through  these  pipes  the 
blood  must  be  pumped 
and  distributed  to  the 
whole  body.  Then  we 
must  have  a  set  of  return 
pipes  by  which  the  blood, 
after  it  has  carried  nour- 
ishment to  the  tissues, 
and  received  waste  mat- 
ters from  them,  shall  be 
brought  back  to  the  cen- 
tral pumping  station,  to 
be  used  again.  We  must 
have  also  some  apparatus 
to  purify  the  blood  from 
the  waste  matter  it  has 
collected. 

This  central  pump  is 

the    heart.        The    pipes  FIG.  68. -Anterior  View  of  the  Heart. 

leading  from  it  and  grad-  A-  suPerior  vena  cava;  B|  right  auride;  C|  riglf 

ventricle  ;  D,  left  ventricle  ;  E,  left  auricle  ;  F,  pul- 
Ually  growing  Smaller  and        moharyvein;    H,  pulmonary  artery;    K,  aorta;    L, 

smaller  are  the  arteries.      right  subclavian  arteir;  M,  right  common  carotid 

artery ;    N ,  left  common  carotid  artery. 

The  very  minute  vessels 

into  which  they  are  at  last  subdivided  are  capillaries.  The 
pipes  which  convey  the  blood  back  to  the  heart  are  the  veins. 
Thus,  the  arteries  end  in  the  tissues  in  fine,  hair-like  vessels,  the 
capillaries  ;  and  the  veins  begin  in  the  tissues  in  exceedingly 


1 76 


PRACTICAL    PHYSIOLOGY. 


small  tubes,  —  the  capillaries.  Of  course,  there  can  be  no 
break  in  the  continuity  between  the  arteries  and  the  veins. 
The  apparatus  of  circulation  is  thus  formed  by  the  heart,  the 
arteries,  the  capillaries,  and  the  veins. 

184.  The  Heart.  The  heart  is  a  pear-shaped,  muscular 
organ  roughly  estimated  as  about  the  size  of  the  person's 
closed  fist.  It  lies  in  the  chest  behind  the  breastbone,  and  is 
lodged  between  the  lobes  of  the  lungs,  which  partly  cover  it. 
In  shape  the  heart  resembles  a  cone,  the  base  of  which  is 
directed  upwards,  a  little  backwards,  and  to  the  right  side, 
while  the  apex  is  pointed  downwards,  forwards,  and  to  the  left 
side.  During  life,  the  apex  of  the  heart  beats  against  the 
chest  wall  in  the  space  between  the  fifth  and  sixth  ribs,  and 
about  an  inch  and  a  half  to  the  left  of  the  middle  line  of  the 
body.  The  beating  of  the  heart  can  be  readily  felt,  heard,  and 
often  seen  moving  the  chest  wall  as  it  strikes  against  it. 

The  heart  does  not  hang  free  in  the  chest,  but  is  suspended 
and  kept  in  position  to  some  extent  by  the  great  vessels  con- 
nected with  it.  It  is  enclosed  in  a 
bell-shaped  covering  called  the  peri- 
cardium. This  is  really  double,  with 
two  layers,  one  over  another.  The  inner 
or  serous  layer  covers  the  external  sur- 
face of  the  heart,  and  is  reflected  back 
upon  itself  in  order  to  form,  like  all 
membranes  of  this  kind,  a  sac  without 

FIG.  69.  —  Diagram  illustrat-  ,      „.      ,          ,  .     , ,  , 

ing  the  structure  of  a  Se-     an  opening.1     The  heart  is  thus  covered 

1  Serous  Membranes.  —  The  serous  membranes 
form  shut  sacs,  of  which  one  portion  is  applied  to  the 
walls  of  the  cavity  which  it  lines ;  the  other  is  reflected 
over  the  surface  of  the  organ  or  organs  contained  in 
the  cavity.  The  sac  is  completely  closed,  so  that  no 
communication  exists  between  the  serous  cavity  and 
the  parts  in  its  neighborhood.  The  various  serous 
membranes  are  the  pleura  which  envelops  the  lungs ; 


rous  Membrane. 
A,  the  viscus,  or  organ,  enveloped 
by  serous  membrane;  B,  layer 
of  membrane  lining  cavity  ;  C , 
membrane  reflected  to  envelop 
viscus ;  D,  outer  layer  of  vis- 
cus, with  blood-vessels  at  E 
communicating  with  the  gen- 
eral circulation. 


THE    BLOOD    AND    ITS    CIRCULATION. 

by  the  pericardial  sac,  but  is  not  contained  inside  its  cavity. 
The  space  between  the  two  membranes  is  filled  with  serous 
fluid.  This  fluid  permits  the  heart  and  the  pericardium  to  glide 
upon  one  another  with  the  least  possible  amount  of  friction.1 

The  heart  is  a  hollow  organ,  but  the  cavity  is  divided  into 
two  parts  by  a  muscular  partition  forming  a  left  and  a  right  side, 
between  which  there  is  no  communication.  These  two  cavities 
are  each  divided  by  a  horizontal  partition  into  an  upper  and  a 
lower  chamber.  These  partitions,  however,  include  a  set  of 
valves  which  open  like  folding  doors  between  the  two  rooms. 
If  these  doors  are  closed  there  are  two  separate  rooms,  but  if 
open  there  is  practically  only  one  room.  The  heart  thus  has 
four  chambers,  two  on  each  side.  The  two  upper  chambers  are 
called  auricles  from  their  supposed  resemblance  to  the  ear. 
The  two  lower  chambers  are  called  ventricles,  and  their  walls 
form  the  chief  portion  of  the  muscular  substance  of  the  organ. 
There  are,  therefore,  the  right  and  left  auricles,  with  their  thin, 
soft  walls,  and  the  right  and  left  ventricles,  with  their  thick  and 
strong  walls. 

185.  The  Valves  of  the  Heart.  The  heart  is  a  valvular 
pump,  which  works  on  mechanical  principles,  the  motive  power 
being  supplied  by  the  contraction  of  its  muscular  fibers.  Re- 
garding the  heart  as  a  pump,  its  valves  assume  great  impor- 
tance. They  consist  of  thin,  but  strong,  triangular  folds  of 
tough  membrane  which  hang  down  from  the  edges  of  the  pas- 
sages into  the  ventricles.  They  may  be  compared  to  swinging 
curtains  which,  by  opening  only  one  way,  allow  the  blood  to  flow 

the  pericardium  which  surrounds  the  heart ;  the  peritoneum  which  invests  the 
viscera  of  the  abdomen,  and  the  arachnoid  in  the  spinal  canal  and  cranial  cavity. 
In  health  the  serous  membranes  secrete  only  sufficient  fluid  to  lubricate  and  keep  soft 
and  smooth  the  opposing  surfaces. 

1  A  correct  idea  may  be  formed  of  the  arrangement  of  the  pericardium  around  the 
heart  by  recalling  how  a  boy  puts  on  and  wears  his  toboggan  cap.  The  pericardium 
encloses  the  heart  exactly  as  this  cap  covers  the  boy's  head. 


178 


PRACTICAL   PHYSIOLOGY. 


FIG.  70.  —  Lateral  Section  of  the  Right  Chest. 
(Showing  the  relative  position  of  the  heart 
and  its  great  vessels,  the  oesophagus  and 
trachea.) 

A,  inferior  constrictor  muscle  (aids  in  conveying 
food  down  the  oesophagus);  B,  resophagus;  C, 
section  of  the  right  bronchus  ;  D,  two  right  pul- 
monary veins ;  E,  great  azygos  vein  crossing 
oesophagus  and  right  bronchus  to  empty  into 
the  superior  vena  cava;  F,  thoracic  duct;  H, 
thoracic  aorta ;  K,  lower  portion  of  oesophagus 
passing  through  the  diaphragm ;  L,  diaphragm 
as  it  appears  in  sectional  view,  enveloping  the 
heart;  M,  inferior  vena  cava  passing  through 
diaphragm  and  emptying  into  auricle  ;  N,  right 
auricle  ;  O,  section  of  right  branch  of  the  pul- 
monary artery  ;  P,  aorta ;  R,  superior  vena  cava ; 
S,  trachea. 


from  the  auricles  to  the 
ventricles,  but  by  instantly 
folding  back  prevent  its  re- 
turn. 

The  valve  on  the  right 
side  is  called  the  tricuspid, 
because  it  consists  of  three 
little  folds  which  fall  over 
the  opening  and  close  it, 
being  kept  from  falling  too 
far  by  a  number  of  slender 
threads  called  chordae  ten- 
dinae.  The  valve  on  the 
left  side,  called  the  mitral, 
from  its  fancied  resem- 
blance to  a  bishop's  mitre, 
consists  of  two  folds  which 
close  together  as  do  those 
of  the  tricuspid  valve. 

The  slender  cords  which 
regulate  the  valves  are  only 
just  long  enough  to  allow 
the  folds  to  close  together, 
and  no  force  of  the  blood 
pushing  against  the  valves 
can  send  them  farther  back, 
as  the  cords  will  not  stretch. 
The  harder  the  blood  in 
the  ventricles  pushes  back 
against  the  valves,  the 
tighter  the  cords  become, 
and  the  closer  the  folds  are 
brought  together,  until  the 
way  is  completely  closed. 


THE    BLOOD    AND    ITS    CIRCULATION. 


179 


From  the  right  ventricle  a  large  vessel  called  the  pulmonary 
artery  passes  to  the  lungs,  and  from  the  left  ventricle  a  large 
vessel  called  the  aorta  arches  out  to  the  general  circulation  of 
the  body.  The  openings  from  the  ventricles  into  these  vessels 
are  guarded  by  the  semilunar 
valves.  Each  valve  has  three 
folds,  each  half-moon -shaped, 
hence  the  name  semilunar. 
These  valves,  when  shut,  pre- 
vent any  backward  flow  of  the 
blood  on  the  right  side  between 
the  pulmonary  artery  and  the 
right  ventricle,  and  on  the  left 
side  between  the  aorta  and 
the  left  ventricle. 

186.  General  Plan  of  the 
Blood-vessels  Connected  with 
the  Heart.  There  are  numer- 
ous blood-vessels  connected 
with  the  heart,  the  relative 
position  and  the  use  of  which 
must  be  understood.  The  two 
largest  veins  in  the  body,  the 
superior  vena  cava  and  the 
inferior  vena  cava,  open  into 
the  right  auricle.  These  two 
veins  bring  venous  blood  from 
all  parts  of  the  body,  and  pour  it  into  the  right  auricle,  whence 
it  passes  into  the  right  ventricle. 

From  the  right  ventricle  arises  one  large  vessel,  the  pul- 
monary artery,  which  soon  divides  into  two  branches  of  nearly 
equal  size,  one  for  the  right  lung,  the  other  for  the  left.  Each 
branch,  having  reached  its  lung,  divides  and  subdivides  again 


FIG.  71.—  Right  Cavities  of  the  Heart. 

A,  aorta;  B,  superior  vena  cava;  C,  C,  right 
pulmonary  veins  ;  D,  inferior  vena  cava ; 
E,  section  of  coronary  vein  ;  F,  right  ven- 
tricular cavity  ;  H,  posterior  curtain  of  the 
tricuspid  valve  ;  K,  right  auricular  cavity ; 
M,  fossa  ovalis,  oval  depression,  partition 
between  the  auricles  formed  after  birth. 


ISO  PRACTICAL    PHYSIOLOGY. 

and  again,  until  it  ends  in  hair-like  capillaries,  which  form  a 
very  fine  network  in  every  part  of  the  lung.  Thus  the  blood 
is  pumped  from  the  right  ventricle  into  the  pulmonary  artery, 
and  distributed  throughout  the  two  lungs  (Figs.  86  and  88). 

We  will  now  turn  to  the  left  side  of  the  heart,  and  notice 
the  general  arrangement  of  its  great  vessels.  Four  veins, 
called  the  pulmonary  veins,  open  into  the  left  auricle,  two 
from  each  lung.  These  veins  start  from  very  minute  vessels, 
the  continuation  of  the  capillaries  of  the  pulmonary  artery. 
They  form  larger  and  larger  vessels  until  they  become  two 
large  veins  in  each  lung,  and  pour  their  contents  into  the  left 
auricle.  Thus  the  pulmonary  artery  carries  venous  blood  from 
the  right  ventricle  to  the  lungs,  as  the  pulmonary  veins  carry 
arterial  blood  from  the  lungs  to  the  left  auricle. 

From  the  left  ventricle  springs  the  largest  arterial  trunk  in 
the  body,  over  one-half  of  an  inch  in  diameter,  called  the 
aorta.  From  the  aorta  other  arteries  branch  off  to  carry  the 
blood  to  all  parts  of  the  body,  only  to  be  again  brought  back 
by  the  veins  to  the  right  side,  through  the  cavities  of  the 
ventricles.  We  shall  learn  in  Chapter  VIII.  that  the  main 
object  of  pumping  the  blood  into  the  lungs  is  to  have  it  puri- 
fied from  certain  waste  matters  which  it  has  taken  up  in  its 
course  through  the  body,  before  it  is  again  sent  on  its  journey 
from  the  left  ventricle. 

187.  The  Arteries.  The  blood-vessels  are  flexible  tubes 
through  which  the  blood  is  borne  through  the  body.  There 
are  three  kinds,  —  the  arteries,  the  veins,  and  the  capillaries, 
and  these  differ  from  one  another  in  various  ways. 

The  arteries  are  the  highly  elastic  and  extensible  tubes 
which  carry  the  pure,  fresh  blood  outwards  from  the  heart  to 
all  parts  of  the  body.  They  may  all  be  regarded  as  branches 
of  the  aorta.  After  the  aorta  leaves  the  left  ventricle  it  rises 
towards  the  neck,  but  soon  turns  downwards,  making  a  curve 
known  as  the  arch  of  the  aorta. 


THE    BLOOD    AND    ITS    CIRCULATION. 


181 


From  the  arch  are  given  off  the  arteries  which  supply  the 
head  and  arms  with  blood.  These  are  the  two  carotid  arteries, 
which  run  up  on  each  side  of  the  neck  to  the  head,  and  the 
two  subclavian  arteries,  which  pass  beneath  the  collar  bone  to 
the  arms.  This  great  arterial 
trunk  now  passes  down  in  front 
of  the  spine  to  the  pelvis,  where 
it  divides  into  two  main  branches, 
which  supply  the  pelvis  and  the 
lower  limbs. 

The  descending  aorta,  while 
passing  downwards,  gives  off 
arteries  to  the  different  tissues 
and  organs.  Of  these  branches 
the  chief  are  the  coeliac  artery, 
which  subdivides  into  three  great 
branches,  —  one  each  to  supply 
the  stomach,  the  liver,  and  the 
spleen ;  then  the  renal  arteries, 
one  to  each  kidney;  and  next  two 
others,  the  mesenteric  arteries,  to 
the  intestines.  The  aorta  at  last 
divides  into  two  main  branches,  FIG.  72.  —  Left  Cavities  of  the  Heart, 
the  common  iliac  arteries,  which,  A,  B,  right  pulmonary  veins ;  with  s, 
by  their  subdivisions,  furnish  the 
-arterial  vessels  for  the  pelvis  and 
the  lower  limbs. 

The  flow  of  blood  in  the 
arteries  is  caused  by  the  muscular  force  of  the  heart,  aided  by 
the  elastic  tissues  and  muscular  fibers  of  the  arterial  walls,  and 
to  a  certain  extent  by  the  muscles  themselves.  Most  of  the 
great  arterial  trunks  lie  deep  in  the  fleshy  parts  of  the  body ; 
but  their  branches  are  so  numerous  and  become  so  minute 
that,  with  a  few  exceptions,  they  penetrate  all  the  tissues  of  the 


openings  of  the  veins ;  E,  D,  C,  aortic 
valves  ;  R,  aorta  ;  P,  pulmonary  artery  ; 
O,  pulmonic  valves;  H,  mitral  valve;. 
K,  columnae  carnceae  ;  M,  right  ventric- 
ular cavity;  N,  interventricular  septum. 


1  82 


PRACTICAL    PHYSIOLOGY. 


body,  —  so  much  so,  that  the  point  of  the  finest  needle  cannot 
be  thrust  into  the  flesh  anywhere  without  wounding  one  or 
more  little  arteries  and  thus  drawing  blood. 

188.  The  Veins.  The  veins  are  the  blood-vessels  which 
carry  the  impure  blood  from  the  various  tissues  of  the  body  to 
the  heart.  They  begin  in  the  minute  capillaries  at  the  extremi- 
ties of  the  four  limbs,  and  everywhere  throughout  the  body, 
and  passing  onwards  toward  the  heart,  receive  constantly 
fresh  accessions  on  the  way  from  myriad 
other  veins  bringing  blood  from  other 
wayside  capillaries,  till  the  central  veins 
gradually  unite  into  larger  and  larger 
vessels  until  at  length  they  form  the  two 
great  vessels  which  open  into  the  right 
auricle  of  the  heart. 

These  two  great  venous  trunks  are 
the  inferior  vena  cava,  bringing  the 
blood  from  the  trunk  and  the  lower 
limbs,  and  the  superior  vena  cava, 

».»  the  head  and 

These  two  large  trunks 


FlG-73- 


gitudinai  section  of  a  vein, 

showing  the  valves  closed. 


the  upper  limbs. 

meet    ^     they 

The  four  pulmonary  veins,  as  we  have  "'learned,  carry  the 
arterial  blood  from  the  lungs  to  the  left  auricle. 

A  large  vein  generally  accompanies  its  corresponding  artery, 
but  most  veins  lie  near  the  surface  of  the  body,  just  beneath 
the  skin.  They  may  be  easily  seen  under  the  skin  of  the  hand 
and  forearm,  especially  in  aged  persons.  If  the  arm  of  a 
young  person  is  allowed  to  hang  down  a  few  moments,  and 
then  tightly  bandaged  above  the  elbow  to  retard  the  return  of 
the  blood,  the  veins  become  large  and  prominent. 

The  walls  of  the  larger  veins,  unlike  arteries,  contain  but  little 
of  either  elastic  or  muscular  tissue  ;  hence  they  are  thin,  and 


THE    BLOOD    AND    ITS    CIRCULATION. 


when  empty  collapse.  The  inner  surfaces  of  many  of  the  veins 
are  supplied  with  pouch-like  folds,  or  pockets,  which  act  as 
valves  to  impede  the  backward  flow  of  the  blood,  while  they 
do  not  obstruct  blood  flowing  forward  toward  the  heart.  These 
valves  can  be  shown  by  letting  the  forearm  hang  down,  and 
sliding  the  finger  upwards  over  the  veins  (Fig.  73). 

The  veins  have  no  force-pump,  like  the  arteries,  to  propel 
their  contents  towards  their  destination.  The  onward  flow  of 
the  blood  in  them  is  due  to  various 
causes,  the  chief  being  the  pressure 
behind  of  the  blood  pumped  into 
the  capillaries.  Then  as  the  pocket- 
like  valves  prevent  the  backward 
flow  of  the  blood,  the  pressure  of 
the  various  muscles  of  the  body 
urges  along  the  blood,  and  thus 
promotes  the  onward"  flow. 

The  forces  which  drive  the  blood 
through  the  arteries  are  sufficient  to 
carry  the  blood  on  through  the  capillaries.  It  is  calculated 
that  the  onward  flow  in  the  capillaries  is  about  ^V  to  53  °f  an 
inch  in  a  second,  while  in  the  arteries  the  blood  current  flows 
about  1 6  inches  in  a  second,  and  in  the  great  veins  about  4 
inches  every  second. 


189.  The  Capillaries.  The  capillaries  are  the  minute, 
hair-like  tubes,  with  very  thin  walls,  which  form  the  connection 
between  the  ending  Of  the  finest  arteries  and  the  beginning  of 
the  smallest  veins.  They  are  distributed  through  every  tissue 
of  the  body,  except  the  epidermis  and  its  products,  the  epithe- 
lium, the  cartilages,  and  the  substance  of  the  teeth.  In  fact, 
the  capillaries  form  a  network  of  the  tiniest  blood-vessels,  so 
minute  as  to  be  quite  invisible,  at  least  one-fourth  smaller  than 
the  finest  line  visible  to  the  naked  eye. 


FIG.  74.  —  The  Structure  of 
Capillaries. 

Capillaries  of  various  sizes,  showing 
cells  with  nuclei. 


184  PRACTICAL  PHYSIOLOGY. 

The  capillaries  serve  as  a  medium  to  transmit  the  blood  from 
the  arteries  to  the  veins ;  and  it  is  through  them  that  the  blood 
brings  nourishment  to  the  surrounding  tissues.  In  brief,  we 
may  regard  the  whole  body  as  consisting  of  countless  groups 
of  little  islands  surrounded  by  ever-flowing  streams  of  blood. 
The  walls  of  the  capillaries  are  of  the  most  delicate  structure, 
consisting  of  a  single  layer  of  cells  loosely  connected.  Thus 
there  is  allowed  the  most  free  interchange  between  the  blood 
and  the  tissues,  through  the  medium  of  the  lymph. 

The  number  of  the  capillaries  is  inconceivable.  Those  in 
the  lungs  alone,  placed  in  a  continuous  line,  would  reach  thou- 
sands of  miles.  The  thin  walls  of  the  capillaries  are  admirably 
adapted  for  the  important  interchanges  that  take  place  between 
the  blood  and  the  tissues. 

190.  The  Circulation  of  the  Blood.  It  is  now  well  to  study 
the  circulation  as  a  whole,  tracing  the  course  of  the  blood  from 
a  certain  point  until  it  returns  to  the  same  point.  We  may 
conveniently  begin  with  the  portion  of  blood  contained  at  any 
moment  in  the  right  auricle.  The  superior  and  inferior  venae 
cavae  are  busily  filling  the  auricle  with  dark,  impure  blood. 
When  it  is  full,  it  contracts.  The  passage  leading  to  the  right 
ventricle  lies  open,  and  through  it  the  blood  pours  till  the 
ventricle  is  full.  Instantly  this  begins,  in  its  turn,  to  contract. 
The  tricuspid  valve  at  once  closes,  and  blocks  the  way  back- 
ward. The  blood  is  now  forced  through  the  open  semilunar 
valves  into  the  pulmonary  artery. 

The  pulmonary  artery,  bringing  venous*  blood,  by  its  alter- 
nate expansion  and  recoil,  draws  the  blood  along  until  it 
reaches  the  pulmonary  capillaries.  These  tiny  tubes  surround 
the  air  cells  of  the  lungs,  and  here  an  exchange  takes  place. 
The  impure,  venous  blood  here  gives  up  its  debris  in  the  shape 
of  carbon  dioxid  and  water,  and  in  return  takes  up  a  large 
amount  of  oxygen.  Thus  the  blood  brought  to  the  lungs  by 


THE    BLOOD    AND    ITS    CIRCULATION. 


I85 


the  pulmonary  arteries  leaves  the  lungs  entirely  different  in 
character  and  appearance.  This  part  of  the  circulation  is 
often  called  the  lesser  or  pulmonic  circulation. 

The  four  pulmonary  veins  bring  back  bright,  scarlet  blood, 
and  pour  it  into  the  left  auricle  of  the  heart,  whence  it  passes 
through  the  mitral  valve  into  the 
left  ventricle.  As  soon  as  the  left 
ventricle  is  full,  it  contracts.  The 
mitral  valve  instantly  closes  and 
blocks  the  passage  backward  into 
the  auricle ;  the  blood,  having  no 
other  way  open,  is  forced  through 
the  semilunar  valves  into  the 
aorta.  Now  red  in  color  from 
its  fresh  oxygen,  and  laden  with 
nutritive  materials,  it  is  distrib- 
uted by  the  arteries  to  the  various 
tissues  of  the  body.  Here  it  gives 
up  its  oxygen,  and  certain  nutri- 
tive materials  to  build  up  the 
tissues,  and  receives  certain  prod- 
ucts of  waste,  and,  changed  to  a 
purple  color,  passes  from  the  cap- 
illaries into  the  veins. 

All  the  veins  of  the  body,  except 
those  from  the  lungs  and  the  heart 
itself,  unite  into  two  large  veins, 
as  already  described,  which  pour 
their  contents  into  the  right  au- 
ricle of  the  heart,  and  thus  the 
grand  round  of  circulation  is  con- 
tinually maintained.  This  is  called  the  systemic  circulation, 
The  whole  circuit  of  the  blood  is  thus  divided  into  two  por 
tions,  very  distinct  from  each  other. 


FIG.  75.  —  Diagram  illustrating  the 
Circulation. 

1,  right  auricle ;  2,  left  auricle  ;  3,  right 
ventricle  ;  4,  left  ventricle  ;  5,  vena 
cava  superior;  6,  vena  cava  inferior  ; 
7,  pulmonary  arteries,  8,  lungs;  9, 
pulmonary  veins  ;  10,  aorta;  11,  ali- 
mentary canal ;  12,  liver;  13,  hepatic 
artery;  14,  portal  vein  ;  15,  hepatic 
vein. 


1 86  PRACTICAL    PHYSIOLOGY. 

191.  The  Portal  Circulation.  A  certain  part  of  the  sys- 
temic or  greater  circulation  is  often  called  the  portal  cir- 
culation, which  consists  of  the  flow  of  the  blood  from  the 
abdominal  viscera  through  the  portal  vein  and  liver  to  the  he- 
patic vein.  The  blood  brought  to  the  capillaries  of  the 
stomach,  intestines,  spleen,  and  pancreas  is  gathered  into 
veins  which  unite  into  a  single  trunk  called  the  portal  vein. 
The  blood,  thus  laden  with  certain  products  of  digestion,  is 
carried  to  the  liver  by  the  portal  vein,  mingling  with  that  sup- 
plied to  the  capillaries  of  the  same  organ  by  the  hepatic  artery. 
From  these  capillaries  the  blood  is  carried  by  small  veins  which 
unite  into  a  large  trunk,  the  hepatic  vein,  which  opens  into 
the  inferior  vena  cava.  The  portal  circulation  is  thus  not  an 
independent  system,  but  forms  a  kind  of  loop  on  the  systemic 
circulation. 

The  lymph-current  is  in  a  sense  a  slow  and  stagnant  side 
stream  of  the  blood  circulation ;  for  substances  are  constantly 
passing  from  the  blood-vessels  into  the  lymph  spaces,  and 
returning,  although  after  a  comparatively  long  interval,  into 
the  blood  by  the  great  lymphatic  trunks. 

Experiment  90.  To  illustrate  the  action  of  the  heart,  and  how  it  pumps 
the  blood  in  only  one  direction.  Take  a  Davidson  or  Household  rubber 
syringe.  Sink  the  suction  end  into  water,  and  press  the  bulb.  As  you  let 
the  bulb  expand,  it  fills  with  water ;  as  you  press  it  again,  a  valve  prevents 
the  water  from  flowing  back,  and  it  is  driven  out  in  a  jet  along  the  other 
pipe.  The  suction  pipe  represents  the  veins ;  the  bulb,  the  heart ;  and 
the  tube  end,  out  of  which  the  water  flows,  the  arteries. 

NOTE.  The  heart  is  not  nourished  by  the  blood  which  passes  through  it.  The 
muscular  substance  of  the  heart  itself  is  supplied  with  nourishment  by  two  little 
arteries  called  the  coronary  arteries,  which  start  from  the  aorta  just  above  two 
of  the  semilunar  valves.  The  blood  is  returned  to  the  right  auricle  (not  to  either  of 
the  venae  cavae)  by  the  coronary  vein. 

The  longest  route  a  portion  of  blood  may  take  from  the  moment  it  leaves  the  left 
ventricle  to  the  moment  it  returns  to  it,  is  through  the  portal  circulation.  The  short- 
est possible  route  is  through  the  substance  of  the  heart  itself.  The  mean  time  which 
the  blood  requires  to  make  a  complete  circuit  is  about  23  seconds. 


THE    BLOOD    AND    ITS    CIRCULATION.  l8/ 

192.  The  Rhythmic  Action  of  the  Heart.     To  maintain  a  steady 
flow  of  blood  throughout  the  body  the  action  of  the  heart  must  be 
regular  and  methodical.     The  heart  does  not  contract  as  a  whole. 
The  two  auricles  contract  at  the  same  time,  and  this  is  followed  at 
once  by  the  contraction  of  the  two  ventricles.     While  the  ventricles 
are  contracting,  the  auricles  begin  to  relax,  and  after  the  ventricles 
contract  they  also  relax.     Now  comes  a  pause,  or  rest,  after  which 
the  auricles  and  ventricles  contract  again  in  the  same  order  as  be- 
fore, and  their  contsactions  are  followed  by  the  same  pause  as  before. 
These  contractions  and  relaxations  of  the  various  parts  of  the  heart 
follow  one  another  so  regularly  that  the  result  is  called  the  rhythmic 
action  of  the  heart. 

The  average  number  of  beats  of  the  heart,  under  normal  conditions, 
is  from  65  to  75  per  minute.  Now  the  time  occupied  from  the  instant 
the  auricles  begin  to  contract  until  after  the  contraction  of  the  ventri- 
cles and  the  pause,  is  less  than  a  second.  Of  this  time  one-fifth  is 
occupied  by  the  contraction  of  the  auricles,  two-fifths  by  the  contrac- 
tion of  the  ventricles,  and  the  time  during  which  the  whole  heart  is 
at  rest  is  two-fifths  of  the  period. 

193.  Impulse  and  Sounds  of  the  Heart.     The  rhythmic 
action  of  the  heart  is  attended  with  various  occurrences  worthy 
of  note.     If  the  hand  be  laid  flat  over  the  chest  wall  on  the 
left,  between  the  fifth  and  sixth  ribs,  the  heart  will  be  felt  beat- 
ing.    This  movement  is  known  as  the  beat  or  impulse  of  the 
heart,  and  can  be  both  seen  and  felt  on  the  left  side.     The 
heart-beat  is  unusually  strong  during  active  bodily  exertion, 
and  under  mental  excitement. 

The  impulse  of  the  heart  is  due  to  the  striking  of  the  lower, 
tense  part  of  the  ventricles  —  the  apex  of  the  heart  —  against 
the  chest  wall  at  the  moment  of  their  vigorous  contraction. 
It  is  important  for  the  physician  to  know  the  exact  place  where 
the  heart-beat  should  be  felt,  for  the  heart  may  be  displaced 
by  disease,  and  its  impulse  would  indicate  its  new  position. 

Sounds  also  accompany  the  heart's  action.  If  the  ear  be 
applied  over  the  region  of  the  heart,  two  distinct  sounds  will 


i88 


PRACTICAL    PHYSIOLOGY. 


be  heard  following  one  another  with  perfect  regularity.  Their 
character  may  be  tolerably  imitated  by  pronouncing  the  sylla- 
bles lubb,  dup.  One  sound  is  heard  immediately  after  the  other, 
then  there  is  a  pause,  then  come  the  two  sounds  again.  The 

first  is  a  dull,  muffled  sound, 
known  as  the  "first  sound," 
followed  at  once  by  a  shorter 
and  sharper  sound,  known 
as  the  "second  sound"  of 
the  heart. 

The  precise  cause  of  the 
first  sound  is  still  doubtful, 
but  it  is  made  at  the  moment 
the  ventricles  contract.  The 
second  sound  is,  without 
doubt,  caused  by  the  sudden 
closure  of  the  semilunar 
valves  of  the  pulmonary  art- 
ery and  the  aorta,  at  the 
moment  when  the  contrac- 
tion of  the  ventricles  is  com- 
pleted. 

The  sounds  of  the  heart 
are  modified  or  masked  by 


FIG.  76.  —  Muscular  Fibers  of  the 

Ventricles. 

A,  superficial  fibers  common  to  both  ventricles ; 
B,  fibers  of  the  left  ventricle  ;   C,  deep  fibers 


passing  upwards  toward  the  base  of  the  heart;    blowing  "murmurs"  when  the 
D,  fibers  penetrating  the  left  ventricle. 

cardiac  orifices  or  valves  are 

roughened,  dilated,  or  otherwise  affected  as  the  result  of  disease. 
Hence  these  new  sounds  may  often  afford  indications  of  the  great- 
est importance  to  physicians  in  the  diagnosis  of  heart-disease. 

194.  The  Nervous  Control  of  the  Heart.  The  regular, 
rhythmic  movement  of  the  heart  is  maintained  by  the  action 
of  certain  nerves.  In  various  places  in  the  substance  of  the 
heart  are  masses  of  nerve  matter,  called  ganglia.  From  these 


THE    BLOOD    AND    ITS    CIRCULATION.  1 89 

ganglia  there  proceed,  at  regular  intervals,  discharges  of  nerve 
energy,  some  of  which  excite  movement,  while  others  seem  to 
restrain  it.  The  heart  would  quickly  become  exhausted  if  the 
exciting  ganglia  had  it  all  their  own  way,  while  it  would  stand 
still  if  the  restraining  ganglia  had  full  sway.  The  influence  of 
one,  however,  modifies  the  other,  and  the  result  is  a  moderate 
and  regular  activity  of  the  heart. 

The  heart  is  also  subject  to  other  nerve  influences,  but  from 
outside  of  itself.  Two  nerves  are  connected  with  the  heart,  the 
pneumogastric  and  the  sympathetic  (sees.  271  and  265). 
The  former  appears  to  be  connected  with  the  restraining  gan- 
glia;  the  latter  with  the  exciting  ganglia.  Thus,  if  a  person 
were  the  subject  of  some  emotion  which  caused  fainting,  the 
explanation  would  be  that  the  impression  had  been  conveyed 
to  the  brain,  and  from  the  brain  to  the  heart  by  the  pneumo- 
gastric nerves.  The  result  would  be  that  the  heart  for  an 
instant  ceases  to  beat.  Death  would  be  the  result  if  the  nerve 
influence  were  so  great  as  to  restrain  the  movements  of  the 
heart  for  any  appreciable  time. 

Again,  if  the  person  were  the  subject  of  some  emotion  by  which 
the  heart  were  beating  faster  than  usual,  it  would  mean  that  there 
was  sent  from  the  brain  to  the  heart  by  the  sympathetic  nerves 
the  impression  which  stimulated  it  to  increased  activity. 

195.  The  Nervous  Control  of  the  Blood-vessels.  The  tone 
and  caliber  of  the  blood-vessels  are  controlled  by  certain  vaso- 
motor  nerves,  which  are  distributed  among  the  muscular  fibers 
of  the  walls.  These  nerves  are  governed  from  a  center  in  the 
medulla  oblongata,  a  part  of  the  brain  (sec.  270).  If  the 
nerves  are  stimulated  more  than  usual,  the  muscular  walls  con- 
tract, and  the  quantity  of  the  blood  flowing  through  them  and 
the  supply  to  the  part  are  diminished.  Again,  if  the  stimulus 
is  less  than  usual,  the  vessels  dilate,  and  the  supply  to  the  part 
is  increased. 


PRACTICAL    PHYSIOLOGY. 

Now  the  vaso-motor  center  may  be  excited  to  increased 
activity  by  influences  reaching  it  from  various  parts  of  the 
body,  or  even  from  the  brain  itself.  As  a  result,  the  nerves 
are  stimulated,  and  the  vessels  contract.  Again,  the  normal 
influence  of  the  vaso-motor  center  may  be  suspended  for  a 
time  by  what  is  known  as  the  inhibitory  or  restraining  effect. 
The  result  is  that  the  tone  of  the  blood-vessels  becomes  dimin- 
ished, and  their  channels  widen. 

The  effect  of  this  power  of  the  nervous  system  is  to  give  it 
a  certain  control  over  the  circulation  in  particular  parts. 
Thus,  though  the  force  of  the  heart  and  the  general  average 
blood-pressure  remain  the  same,  the  state  of  the  circulation 
may  be  very  different  in  different  parts  of  the  body.  The  im- 
portance of  this  local  control  over  the  circulation  is  of  the 
utmost  significance.  Thus  an  organ  at  work  needs  to  be  more 
richly  supplied  with  blood  than  when  at  rest.  For  example, 
when  the  salivary  glands  need  to  secrete  saliva,  and  the 
stomach  to  pour  out  gastric  juice,  the  arteries  that  supply 
these  organs  are  dilated,  and  so  the  parts  are  flushed  with  an 
extra  supply  of  blood,  and  thus  are  aroused  to  greater  activity. 

Again,  the  ordinary  supply  of  blood  to  a  part  may  be  les- 
sened, so  that  the  organ  is  reduced  to  a  state  of  inactivity,  as 
occurs  in  the  case  of  the  brain  during  sleep.  We  have  in  the 
act  of  blushing  a  visible  example  of  sudden  enlargement  of  the 
smaller  arteries  of  the  face  and  neck,  called  forth  by  some 
mental  emotion  which  acts  on  the  vaso-motor  center  and 

Experiment  91.  Hold  up  the  ear  of  a  white  rabbit  against  the  light 
while  the  animal  is  kept  quiet  and  not  alarmed.  The  red  central  artery 
can  be  seen  coursing  along  the  translucent  organ,  giving  off  branches 
which  by  subdivision  become  too  small  to  be  separately  visible,  and  the 
whole  ear  has  a  pink  color  and  is  warm  from  the  abundant  blood  flowing 
through  it.  Attentive  observation  will  show  also  that  the  caliber  of  the 
main  artery  is  not  constant ;  at  somewhat  irregular  periods  of  a  minute  or 
more  it  dilates  and  contracts  a  little. 


THE    BLOOD    AND    ITS    CIRCULATION. 


RADIAL    ARTERY- 
RADIAL    VEIN 


FIG.  77.  — Some  of  the  Principal  Organs  of  the  Chest  and  Abdomen.     (Blood- 
vessels on  the  left ;  muscles  on  the  right.) 


192 


PRACTICAL    PHYSIOLOGY. 


diminishes  its  activity.  The  reverse  condition  occurs  in  the 
act  of  turning  pale.  Then  the  result  of  the  mental  emotion 
is  to  cause  the  vaso-motor  nerves  to  exercise  a  more  powerful 
control  over  the  capillaries,  thereby  closing  them,  and  thus 

shutting  off  the  flow  of  blood. 
In  brief,  all  over  the  body, 
the  nervous  system,  by  its  vaso- 
motor  centers,  is  always  super- 
vising and  regulating  the  distri- 
bution of  blood  in  the  body, 
sending  now  more  and  now 
less  to  this  or  that  part. 

196.   The  Pulse.    When  the 
FIG.  78.  — Capillary  Blood- Vessels  in  the   finger    is    placed    on    any   part 

Web  of  a  Frog's   Foot,  as  seen  with       r    , ,        u     ,         , 

the  Microscope  °f  the  b°dy  wher6   an  art£ry  1S 

located  near  the  surface,  as,  for 

example,  on  the  radial  artery  near  the  wrist,  there  is  felt  an 
intermittent  pressure,  throbbing  with  every  beat  of  the  heart. 
This  movement,  frequently  visible  to  the  eye,  is  the  result  of 
the  alternate  expansion  of  the  artery  by  the  wave  of  blood, 
and  the  recoil  of  the  arterial  walls  by  their  elasticity.  In  other 
words,  it  is  the  wave  produced  by  throwing  a  mass  of  blood 
into  the  arteries  already  full.  The  blood-wave  strikes  upon 
the  elastic  walls  of  the  arteries,  causing  an  increased  distention, 
followed  at  once  by  contraction.  This  regular  dilatation  and 
rigidity  of  the  elastic  artery  answering  to  the  beats  of  the  heart, 
is  known  as  the  pulse. 

The  pulse  may  be  easily  found  at  the  wrist,  the  temple,  and 
the  inner  side  of  the  ankle.  The  throb  of  the  two  carotid 
arteries  may  be  plainly  felt  by  pressing  the  thumb  and  finger 
backwards  on  each  side  of  the  larynx.  The  progress  of  the 
pulse-wave  must  not  be  confused  with  the  actual  current  of  the 
blood  itself.  For  instance,  the  pulse-wave  travels  at  the  rate 


THE    BLOOD    AND    ITS    CIRCULATION. 


193 


of  about  30  feet  a  second,  and  takes  about  T\^  of  a  second 
to  reach  the  wrist,  while  the  blood  itself  is  from  3  to  5  seconds 
in  reaching  the  same  place. 

The  pulse-wave  may  be  compared  to  the  wave  produced  by 
a  stiff  breeze  on  the  surface  of  a  slowly  moving  stream,  or  the 
jerking  throb  sent  along  a  rope  when  shaken.  The  rate  of  the 
pulse  is  modified  by  age,  fatigue,  posture,  exercise,  stimulants, 
disease,  and  many  other  circum- 
stances. At  birth  the  rate  is  about 
140  times  a  minute,  in  early  in- 
fancy, 120  or  upwards,  in  the 
healthy  adult  between  65  and  75, 
the  most  common  number  being  72. 
In  the  same  individual,  the  pulse  is 
quicker  when  standing  than  when 
lying  down,  is  quickened  by  excite- 
ment, is  faster  in  the  morning, 
and  is  slowest  at  midnight.  In 
old  age  the  pulse  is  faster  than 
in  middle  life;  in  children  it  is  quicker  than  in  adults. 

As  the  pulse  varies  much  in  its  rate  and  character  in  disease, 
it  is  to  the  skilled  touch  of  the  physician  an  invaluable  help  in 
the  diagnosis  of  the  physical  condition  of  his  patient. 

Experiment  92.  To  find  the  pulse.  Grasp  the  wrist  of  a  friend,  press- 
ing with  three  fingers  over  the  radius.  Press  three  fingers  over  the  radius 
in  your  own  wrist,  to  feel  the  pulse. 

Count  by  a  watch  the  rate  of  your  pulse  per  minute,  and  do  the  same 
with  a  friend's  pulse.  Compare  its  characters  with  your  own  pulse. 

Observe  how  the  character  and  frequency  of  the  pulse  are  altered  by 
posture,  muscular  exercise,  a  prolonged,  sustained,  deep  inspiration,  pro- 
longed expiration,  and  other  conditions. 

197.  Effect  of  Alcoholic  Liquors  upon  the  Organs  of  Cir- 
culation. Alcoholic  drinks  exercise  a  destructive  influence 
upon  the  heart,  the  circulation,  and  the  blood  itself.  These 


FIG.  79.  —  Circulation  in  the  Cap- 
illaries, as  seen  with  the  Micro- 
scope. 


194 


PRACTICAL    PHYSIOLOGY. 


vicious  liquids  can  reach  the  heart  only  indirectly,  either 
from  the  stomach  by  the  portal  vein  to  the  liver,  and  thence  to 
the  heart,  or  else  by  way  of  the  lacteals, 
and  so  to  the  blood  through  the  thoracic 
duct.  But  by  either  course  the  route  is 
direct  enough,  and  speedy  enough  to  ac- 
complish a  vast  amount  of  ruinous  work. 

The  influence  of  alcohol  upon  the  heart 
and  circulation  is  produced  mainly  through 
the  nervous  system.    The  inhibitory  nerves, 
as  we  have  seen,  hold  the  heart  in  check, 
exercise  a  restraining  control  over  it,  very 
much  as  the  reins  control  an  active  horse. 
In  health  this  inhibitory  influence  is  pro- 
tective and  sustaining.      But  now  comes 
the  narcotic  invasion  of  alcoholic  drinks, 
which  paralyze  the  inhibitory  nerves,  with 
the  others,  and  at  once  the  uncontrolled 
heart,  like  the   unchecked  steed,  plunges 
on  to  violent  and  often  destructive  results. 
This  action,  because  it  is  quicker,  has 
been  considered  also  a  stronger  action,  and 
the  alcohol  has  therefore  been  supposed  to 
produce  a  stimulating  effect.     But  later  re- 
searches lead  to  the  conclusion  that  the 
effect  of  alcoholic  liquors  is  not  properly 
that  of  a  stimulant,  but  of  a  narcotic  para- 
FIG.  80.- TWO  Principal  tyzant,  and  that  while  it  indeed  quickens, 
Arteries  of  the  Front  of  it  also  really  weakens   the  heart's  action, 
the  Leg  (Anterior  Tibial    Thig  yiew  WQuld  seem  sustained  by  the  fact 
and  Dorsalis  Pedis). 

that  the  more  the  intoxicants  are  pushed, 

the  deeper  are  the  narcotic  and  paralyzing  effects.  After  hav- 
ing obstructed  the  nutritive  and  reparative  functions  of  the  vital 
fluid  for  many  years,  their  effects  at  last  may  become  fatal. 


THE    BLOOD    AND    ITS    CIRCULATION.  1 95 

This  relaxing  effect  involves  not  only  the  heart,  but  also  the 
capillary  system,  as  is  shown  in  the  complexion  of  the  face 
and  the  color  of  the  hands.  In  moderate  drinkers  the  face  is 
only  flushed,  but  in  drunkards  it  is  purplish.  The  flush  attend- 
ing the  early  stages  of  drinking  is,  of  course,  not  the  flush  of 
health,  but  an  indication  of  disease.1 

198.  Effect  upon  the  Heart.     This  forced  overworking  of 
the  heart  which  drives  it  at  a  reckless  rate,  cuts  short  its  periods 
of  rest  and  inevitably  produces  serious  heart-exhaustion.     If 
repeated  and  continued,  it  involves  grave  changes  of  the  struc- 
ture of  the  heart.     The  heart  muscle,  endeavoring  to  compen- 
sate for  the  overexertion,  may  become  much  thickened,  making 
the  ventricles  smaller,  and  so  fail  to  do  its  duty  in  properly 
pumping  forward  the  blood  which  rushes  in  from  the  auricle. 
Or  the  heart  wall  may  by  exhaustion  become  thinner,  making 
the  ventricles  much  too  large,  and  unable  to  send  on  the  cur- 
rent.    In  still  other  cases,  the  heart  degenerates  with  minute 
particles  of  fat  deposited  in  its  structures,  and  thus  loses  its 
power  to  propel  the  nutritive  fluid.     All  three  of  these  con- 
ditions   involve  organic  disease  of  the  valves,  and  all   three 
often  produce  fatal  results. 

199.  Effect  of  Alcohol  on  the  Blood-vessels.     Alcoholic 
liquors  injure  not  only  the  heart,  but  often  destroy  the  blood- 
vessels, chiefly  the  larger  arteries,  as  the  arch  of  the  aorta  or 

1  "  Alcohol  taken  in  small  and  single  doses,  acts  almost  exclusively  on  the  brain 
and  the  blood-vessels  of  the  brain,  whereas  taken  in  large  and  repeated  doses  its 
chief  effects  are  always  nervous  effects.  The  first  effects  of  alcohol  on  the  function 
of  inhibition  are  to  paralyze  the  controlling  nerves,  so  that  the  blood-centers  are 
dilated,  and  more  blood  is  let  into  the  brain.  In  consequence  of  this  flushing  of  the 
brain,  its  nerve  centers  are  asked  to  do  more  work."  —  DR.  T.  S.  CLOUSTON,  Medical 
Superintendent  of  the  'Royal  Asylum,  Edinburgh. 

"  Alcoholic  drinks  prevent  the  natural  changes  going  on  in  the  blood,  and  obstruct 
the  nutritive  and  reparative  functions." —  PROFESSOR  E.  L.  YOUMANS,  well-known 
scientist  and  author  of  Class  Book  of  Chemistry. 


196 


PRACTICAL    PHYSIOLOGY. 


the  basilar  artery  of  the  brain.  In  the  walls  of  these  vessels 
may  be  gradually  deposited  a  morbid  product,  the  result  of 
disordered  nutrition,  sometimes  chalky,  sometimes  bony,  with 

usually  a  dangerous 
dilatation  of  the  tube. 
In  other  cases  the 
vessels  are  weak- 
ened by  an  unnat- 
ural fatty  deposit. 
Though  these  dis- 
ordered conditions 
differ  somewhat,  the 
morbid  results  in  all 
are  the  same.  The 
weakened  and  stiff- 
ened arterial  walls 
lose  the  elastic  spring 
of  the  pulsing  cur- 
rent. The  blood  fails 
to  sweep  on  with  its 
accustomed  vigor. 
At  last,  owing  per- 
haps to  the  pressure, 
against  the  obstruc- 
tion of  a  clot  of 


FIG.  81.  —  Showing  the  Carotid  Artery  and  Jugular 
Vein  on  the  Right  Side,  with  Some  of  their  Main 
Branches.  (Some  branches  of  the  cervical  plexus, 
and  the  hypoglossal  nerve  are  also  shown.) 


some  unusual  strain  of  work  or    passion, 


blood,  or  perhaps  to 
the  enfeebled  vessel 


bursts,  and  death  speedily  ensues  from  a  form  of  apoplexy. 

NOTE.  "  An  alcoholic  heart  loses  its  contractile  and  resisting  power,  both  through 
morbid  changes  in  its  nerve  ganglia  and  in  its  muscle  fibers.  In  typhoid  fever, 
muscle  changes  are  evidently  the  cause  of  the  heart-enfeeblement ;  while  in  diph- 
theria, disturbances  in  innervation  cause  the  heart  insufficiency.  '  If  the  habitual 
use  of  alcohol  causes  the  loss  of  contractile  and  resisting  power  by  impairment  of 
both  the  nerve  ganglia  and  muscle  fibers  of  the  heart,  how  can  it  act  as  a  heart 
tonic?'"  —  DR.  ALFRED  L.  LOOMIS,  Professor  of  Medicine  in  the  Medical  Depart- 
ment of  the  University  of  the  City  of  New  York. 


THE    BLOOD    AND    ITS    CIRCULATION.  1 97 

200.  Other  Results  from  the  Use  of  Intoxicants.  Other 
disastrous  consequences  follow  the  use  of  intoxicants,  and  these 
upon  the  blood.  When  any  alcohol  is  present  in  the  circulation, 
its  greed  for  water  induces  the  absorption  of  moisture  from  the 
red  globules  of  the  blood,  the  oxygen-carriers.  In  consequence 
they  contract  and  harden,  thus  becoming  unable  to  absorb,  as 
theretofore,  the  oxygen  in  the  lungs.  Then,  in  turn,  the  oxida- 


FIG  82.  — The  Right  Axillary 
and  Brachial  Arteries,  with 
Some  of  their  Main  Branches. 


tion  of  the  waste  matter  in  the  tissues  is  prevented  ;  thus  the 
corpuscles  cannot  convey  carbon  dioxid  from  the  capillaries, 
and  this  fact  means  that  some  portion  of  refuse  material,  not 
being  thus  changed  and  eliminated,  must  remain  in  the  blood, 
rendering  it  impure  and  unfit  for  its  proper  use  in  nutrition. 
Thus,  step  by  step,  the  use  of  alcoholics  impairs  the  functions 
of  the  blood  corpuscles,  perverts  nutrition,  and  slowly  poisons 
the  blood. 

NOTE.  "  Destroy  or  paralyze  the  inhibitory  nerve  center,  and  instantly  its  con- 
trolling effect  on  the  heart  mechanism  is  lost,  and  the  accelerating  agent,  being  no 
longer  under  its  normal  restraint,  runs  riot.  The  heart's  action  is  increased,  the  pulse 
is  quickened,  an  excess  of  blood  is  forced  into  the  vessels,  and  from  their  becoming 
engorged  and  dilated  the  face  gets  flushed,  all  the  usual  concomitants  of  a  general 
engorgement  of  the  circulation  being  the  result."  —  DR.  GEORGE  HARLEY,  F.R.S., 
an  eminent  English  medical  author. 


PRACTICAL    PHYSIOLOGY. 

201.  Effect  of  Tobacco  upon  the  Heart.  While  tobacco 
poisons  more  or  less  almost  every  organ  of  the  body,  it  is  upon 
the  heart  that  it  works  its  most  serious  wrong.  Upon  this 
most  important  organ  its  destructive  effect  is  to  depress  and 
paralyze.  Especially  does  this  apply  to  the  young,  whose 
bodies  are  not  yet  knit  into  the  vigor  that  can  brave  invasion. 

The  nicotine  of  tobacco  acts  through  the  nerves  that  control 
the  heart's  action.  Under  its  baneful  influence  the  motions 
of  the  heart  are  irregular,  now  feeble  and  fluttering,  now 
thumping  with  apparently  much  force  :  but  both  these  forms 
of  disturbed  action  indicate  an  abnormal  condition.  Fre- 
quently there  is  severe  pain  in  the  heart,  often  dizziness  with 
gasping  breath,  extreme  pallor,  and  fainting. 

The  condition  of  the  pulse  is  a  guide  to  this  state  of  the 
heart.  In  this  the  physician  reads  plainly  the  existence  of  the 
"  tobacco  heart,"  an  affection  as  clearly  known  among  medical 
men  as  croup  or  measles.  There  are  few  conditions  more  dis- 
tressing than  the  constant  and  impending  suffering  attending  a 
tumultuous  and  fluttering  heart.  It  is  stated  that  one  in  every 
four  of  tobacco-users  is  subject,  in  some  degree,  to  this  dis- 
turbance. Test  examinations  of  a  large  number  of  lads  who 
had  used  cigarettes  showed  that  only  a  very  small  percentage 
escaped  cardiac  trouble.  Of  older  tobacco-users  there  are 
very  few  but  have  some  warning  of  the  hazard  they  invoke. 
Generally  they  suffer  more  or  less  from  the  tobacco  heart, 
and  if  the  nervous  system  or  the  heart  be  naturally  feeble, 
they  suffer  all  the  more  speedily  and  intensely. 

"  The  habitual  use  of  alcohol  produces  a  deleterious  influence  upon  the  whole 
economy.  The  digestive  powers  are  weakened,  the  appetite  is  impaired,  and  the 
muscular  system  is  enfeebled.  The  blood  is  impoverished,  and  nutrition  is  imperfect 
and  disordered,  as  shown  by  the  flabbiness  of  the  skin  and  muscles,  emaciation,  or  an 
abnormal  accumulation  of  fat." —  DR.  AUSTIN  FLINT,  Senior,  formerly  Professor  of 
the  Practice  of  Medicine  in  Bellevue  Medical  College,  and  author  of  many  standard 
medical  works. 

"  The  immoderate  use  of  the  strong  kind  of  tobacco,  which  soldiers  affect,  is  often 
very  injurious  to  them,  especially  to  very  young  soldiers.  It  renders  them  nervous 


THE    BLOOD    AND    ITS    CIRCULATION.  1 99 

and  shaky,  gives  rise  to  palpitation,  and  is  a  factor  in  the  production  of  the  irritable 
or  so-called  "  trotting-heart "  and  tends  to  impair  the  appetite  and  digestion."  — 
London  Lancet. 

"  I  never  smoke  because  I  have  seen  the  most  efficient  proofs  of  the  injurious 
effects  of  tobacco  on  the  nervous  system/'  —  DR.  BROWN-SEQUARD,  the  eminent 
French  physiologist. 

"  Tobacco,  and  especially  cigarettes,  being  a  depressant  upon  the  heart,  should  be 
positively  forbidden." —  DR.  J.  M.  KEATING,  on  "  Physical  Development,"  in  Cyclo- 
pedia of  the  Diseases  of  Children. 

ADDITIONAL   EXPERIMENTS. 

Experiment  93.  Touch  a  few  drops  of  blood  fresh  from  the  finger, 
with  a  strip  of  dry,  smooth,  neutral  litmus  paper,  highly  glazed  to  prevent 
the  red  corpuscles  from  penetrating  into  the  test  paper.  Allow  the  blood 
to  remain  a  short  time  ;  then  wash  it  off  with  a  stream  of  distilled  water, 
when  a  blue  spot  upon  a  red  or  violet  ground  will  be  seen,  indicating  its 
alkaline  reaction,  due  chiefly  to  the  sodium  phosphate  and  sodium  car- 
bonate. 

Experiment  94.  Place  on  a  glass  slide  a  thin  layer  of  defibrinated 
blood ;  try  to  read  printed  matter  through  it.  This  cannot  be  done. 

Experiment  95.  To  make  blood  transparent  or  laky.  Place  in  each  of 
three  test  tubes  two  or  three  teaspoonfuls  of  defibrinated  blood,  obtained 
from  Experiment  89,  labeled  A,  B,  and  C.  A  is  for  comparison.  To  B 
add  five  volumes  of  water,  and  warm  slightly,  noting  the  change  of  color 
by  reflected  and  transmitted  light.  By  reflected  light  it  is  much  darker, 
—  it  looks  almost  black  ;  but  by  transmitted  light  it  is  transparent.  Test 
this  by  looking  at  printed  matter  as  in  Experiment  94. 

Experiment  96.  To  fifteen  or  twenty  drops  of  defibrinated  blood  in  a 
test  tube  (labeled  D)  add  five  volumes  of  a  lo-per-cent  solution  of  common 
salt.  It  changes  to  a  very  bright,  florid,  brick-red  color.  Compare  its  color 
with  A,  B)  and  C.  It  is  opaque. 

Experiment  97.  Wash  away  the  coloring  matter  from  the  twigs  (see 
Experiment  89)  with  a  stream  of  water  until  the  fibrin  becomes  quite  white. 
It  is  white,  fibrous,  and  elastic.  Stretch  some  of  the  fibers  to  show  their 
extensibility ;  on  freeing  them,  they  regain  their  elasticity. 

Experiment  98.  Take  some  of  the  serum  saved  from  Experiment  88 
and  note  that  it  does  not  coagulate  spontaneously.  Boil  a  little  in  a  test 
tube  over  a  spirit  lamp,  and  the  albumen  will  coagulate. 


2OO  PRACTICAL    PHYSIOLOGY. 

Experiment  99.  To  illustrate  in  a  general  "way  that  blood  is  really  a 
mass  of  red  bodies  which  give  the  red  color  to  the  fluid  in  -which  they  float. 
Fill  a  clean  white  glass  bottle  two-thirds  full  of  little  red  beads,  and  then  fill 
the  bottle  full  of  water.  At  a  short  distance  the  bottle  appears  to  be  filled 
with  a  uniformly  red  liquid. 

Experiment  100.  To  show  how  blood  holds  a  mineral  substance  in  solu- 
tion. Put  an  egg-shell  crushed  fine,  into  a  glass  of  water  made  acid  by  a 
teaspoonful  of  muriatic  acid.  After  an  hour  or  so  the  egg-shell  will  dis- 
appear, having  been  dissolved  in  the  acid  water.  In  like  manner  the  blood 
holds  various  minerals  in  solution. 

Experiment  101.  To  hear  the  sounds  of  the  heart.  Locate  the  heart 
exactly.  Note  its  beat.  Borrow  a  stethoscope  from  some  physician. 
Listen  to  the  heart-beat  of  some  friend.  Note  the  sounds  of  your  own 
heart  in  the  same  way. 

Experiment  102.  To  show  how  the  pulse  may  be  studied.  "  The  move- 
ments of  the  artery  in  the  human 
body  as  the  pulse-wave  passes 
through  it  may  be  shown  to  con- 
sist in  a  sudden  dilatation,  fol- 
lowed by  a  slow  contraction, 
interrupted  by  one  or  more  sec- 
ondary dilatations.  This  dem- 
onstration may  be  made  by 
pressing  a  small  piece  of  look- 
ing-glass about  one  centimeter 
square  (?-  of  an  inch)  upon  the 
wrist  over  the  radial  artery,  in 
such  a  way  that  with  each  pulse 
beat  the  mirror  may  be  slightly 
FIG.  83.-  How  the  Pulse  may  be  studied  by  tilted.  If  the  wrist  be  now  held 
Pressing  a  Mirror  over  the  Radial  Artery.  in  such  a  position  that  sunlight 

will  fall  upon  the  mirror,  a  spot 

of  light  will  be  reflected  on  the  opposite  side  of  the  room,  and  its  motion 
upon  the  wall  will  show  that  the  expansion  of  the  artery  is  a  sudden  move- 
ment, while  the  subsequent  contraction  is  slow  and  interrupted." —  BOW- 
DITCH'S  Hints  for  Teachers  of  Physiology. 

Experiment  103.  To  illustrate  the  effect  of  muscular  exercise  in  quick- 
ening the  pulse.  Run  up  and  down  stairs  several  times.  Count  the  pulse 
both  before  and  after.  Note  the  effect  upon  the  rate. 


THE    BLOOD    AND    ITS    CIRCULATION.  2OI 

Experiment  104.  7<?  show  the  action  of  the  elastic  walls  of  the  arteries. 
Take  a  long  glass  or  metal  tube  of  small  caliber.  Fasten  one  end  to  the 
faucet  of  a  water-pipe  (one  in  a  set  bowl  preferred)  by  a  very  short  piece 
of  rubber  tube.  Turn  the  water  on  and  off  alternately  and  rapidly,  to  imi- 
tate the  intermittent  discharge  of  the  ventricles.  The  water  will  flow  from 
the  other  end  of  the  rubber  pipe  in  jets,  each  jet  ceasing  the  moment  the 
water  is  shut  off. 

The  experiment  will  be  more  successful  if  the  rubber  bulb  attached  to 
an  ordinary-  medicine-dropper  be  removed,  and  the  tapering  glass  tube  be 
slipped  on  to  the  outer  end  of  the  rubber  tube  attached  to  the  faucet. 

Experiment  105.  Substitute  a  piece  of  rubber  tube  for  the  glass  tube, 
and  repeat  the  preceding  experiment.  Now  it  will  be  found  that  a  continu- 
ous stream  flows  from  the  tube.  The  pressure  of  water  stretches  the  elas- 
tic tube,  and  when  the  stream  is  turned  off,  the  rubber  recoils  on  the 
water,  and  the  intermittent  flow  is  changed  into  a  continuous  stream. 

Experiment  106.  To  illustrate  some  of  the  phenomena  of  circulation. 
Take  a  common  rubber  bulb  syringe,  of  the  Davidson,  Household,  or  any 
other  standard  make.  Attach  a  piece  of  rubber  tube  about  six  or  eight 
feet  long  to  the  delivery  end  of  the  syringe. 

To  represent  the  resistance  made  by  the  capillaries  to  the  flow  of  blood, 
slip  the  large  end  of  a  common  glass  medicine-dropper  into  the  outer  end 
of  the  rubber  tube.  This  dropper  has  one  end  tapered  to  a  fine  point. 

Place  the  syringe  flat,  without  kinks  or  bends,  on  a  desk  or  table. 
Press  the  bulb  slowly  and  regularly.  The  water  is  thus  pumped  into  the 
tube  in  an  intermittent  manner,  and  yet  it  is  forced  out  of  the  tapering  end 
of  the  glass  tube  in  a  steady  flow. 

Experiment  107.  Take  off  the  tapering  glass  tube,  or,  in  the  place  of 
one  long  piece  of  rubber  tube,  substitute  several  pieces  of  glass  tubing 
connected  together  by  short  pieces  of  rubber  tubes.  The  obstacle  to  the 
flow  has  thus  been  greatly  lessened,  and  the  water  flows  out  in  intermittent 
jets  to  correspond  to  the  compression  of  the  bulb. 


CHAPTER    VIII. 
RESPIRATION. 

202.  Nature  and  Object  of  Respiration.  The  blood,  as  we 
have  learned,  not  only  provides  material  for  the  growth  and 
activity  of  all  the  tissues  of  the  body,  but  also  serves  as  a 
means  of  removing  from  them  the  products  of  their  activity. 
These  are  waste  products,  which  if  allowed  to  remain,  would 
impair  the  health  of  the  tissues.  Thus  the  blood  becomes 
impoverished  both  by  the  addition  of  waste  material,  and  from 
the  loss  of  its  nutritive  matter. 

We  have  shown,  in  the  preceding  chapter,  how  the  blood 
carries  to  the  tissues  the  nourishment  it  has  absorbed  from  the 
food.  We  have  now  to  consider  a  new  source  of  nourishment 
to  the  blood,  viz.,  that  which  it  receives  from  the  oxygen  of 
the  air.  We  are  also  to  learn  one  of  the  methods  by  which 
the  blood  gets  rid  of  poisonous  waste  matters.  In  brief,  we 
are  to  study  the  set  of  processes  known  as  respiration,  by 
which  oxygen  is  supplied  to  the  various  tissues,  and  by  which 
the  principal  waste  matters,  or  chief  products  of  oxidation, 
are  removed. 

Now,  the  tissues  are  continually  feeding  on  the  life-giving 
oxygen,  and  at  the  same  time  are  continually  producing  car- 
bon dioxid  and  other  waste  products.  In  fact,  the  life  of  the 
tissues  is  dependent  upon  a  continual  succession  of  oxidations 
and  deoxidations.  When  the  blood  leaves  the  tissues,  it  is 
poorer  in  oxygen,  is  burdened  with  carbon  dioxid,  and  has  had 
its  color  changed  from  bright  scarlet  to  purple  red.  This  is 
the  change  from  the  arterial  to  venous  conditions  which  has 
been  described  in  the  preceding  chapter. 


RESPIRATION. 


203 


Now,  as  we  have  seen,  the  change  from  venous  to  arterial 
blood  occurs  in  the  capillaries  of  the  lungs,  the  only  means  of 
communication  between  the  pulmonary  arteries  and  the  pul- 
monary veins.  The  blood  in  the  pulmonary  capillaries  is  sep- 
arated from  the  air  only  by  a  delicate  tissue  formed  of  its  own 
wall  and  the  pulmonary  membrane.  Hence  a  gaseous  inter- 
change, the  essential  step  in  respiration,  very  readily  takes 
place  between  the  blood  and  the  air,  by  which  the  latter  gains 
moisture  and  carbon  dioxid,  and  loses  its  oxygen.  These  changes 
in  the  lungs  also  restore  to  the  dark  blood  its  rosy  tint. 

The  only  condition  absolutely  necessary  to  the  purification 
of  the  blood  is  an  organ  having  a  delicate 
membrane,  on  one  side  of  which  is  a  thin 
sheet  of  blood,  while  the  other  side  is 
in  such  contact  with  the  air  that  an  inter- 
change of  gases  can  readily  take  place. 
The  demand  for  oxygen  is,  however,  so 
incessant,  and  the  accumulation  of  carbon 
dioxid  is  so  rapid  in  every  tissue  of  the 
human  body,  that  an  All-Wise  Creator  has 
provided  a  most  perfect  but  complicated 
set  of  machinery  to  effect  this  wonderful 
purification  of  the  blood. 

We  are  now  ready  to  begin  the  study 
of  the  arrangement  and  working  of  the  res- 
piratory apparatus.  With  its  consideration,  we  complete  our 
view  of  the  sources  of  supply  to  the  blood,  and  begin  our  study 
of  its  purification. 

203.  The  Trachea,  or  Windpipe.  If  we  look  into  the  mouth 
of  a  friend,  or  into  our  own  with  a  mirror,  we  see  at  the  back 
part  an  arch  which  is  the  boundary  line  of  the  mouth  proper. 
There  is  just  behind  this  a  similar  limit  for  the  back  part  of 
Lhe  nostrils.  The  funnel-shaped  cavity  beyond,  into  which 


FIG.  84. 

The  Epiglottis. 


204 


PRACTICAL    PHYSIOLOGY. 


both  the  mouth  and  the  posterior  nasal  passages  open,  is 
called  the  pharynx.  In  its  lower  part  are  two  openings. ;  the 
trachea,  or  windpipe,  in  front,  and  the  oesophagus  behind. 
The  trachea  is  surmounted  by  a  box-like  structure  of  carti- 
lage, about  four  and  one- 
half  inches  long,  called  the 
larynx.  The  upper  end 
of  the  larynx  opens  into 
the  pharynx  or  throat,  and 
is  provided  with  a  lid,  — 
the  epiglottis, —  which 
closes  under  certain  cir- 
cumstances (sees.  137  and 
349).  The  larynx  contains 
the  organ  of  voice,  and  is 
more  fully  described  in 
Chapter  XII. 

The  continuation  of  the 
larynx  is  the  trachea,  a 
tube  about  three-fourths  of 
an  inch  in  diameter,  and 
about  four  inches  long. 
It  extends  downwards 
along  the  middle  line  of 
the  neck,  where  it  may 


FIG.  85. —  Larynx,  Trachea,  and  the  Bronchi. 
(Front  view.) 

A,  epiglottis ;  B,  thyroid  cartilage ;  C,  cricoid- 
thyroid  membrane,  connecting  with  the  cricoid 
cartilage  below,  all  forming  the  larynx ;  D,  one 
of  the  rings  of  the  trachea. 


readily    be    felt    in    front, 
below  the  Adam's  apple. 

The  walls  of  the  wind- 
pipe are  strengthened  by 
a  series  of  cartilaginous 
rings,  each  somewhat  the  shape  of  a  horseshoe  or  like  the  letter 
C,  being  incomplete  behind,  where  they  come  in  contact  with 
the  oesophagus.  Thus  the  trachea,  while  always  open  for  the 
passage  of  air,  admits  of  the  distention  of  the  food-passage. 


RKSl'l  RATION. 


205 


204.  The  Bronchial  Tubes.  The  lower  end  of  the  wind- 
pipe is  just  behind  the  upper  part  of  the  sternum,  and  there  it 
divides  into  two  branches,  called  bronchi.  Each  branch  enters 
the  lung  of  its  own  side,  and  breaks  up  into  a  great  number  of 


FIG.  86.—  Relative  Position  of  the  Lungs,  Heart,  and  its  Great  Vessels, 

A,  left  ventricle  ;  B,  right  ventricle;  C,  left  auricle;  D,  right  auricle;  E.  superior  vena 
cava;  F,  pulmonary  artery;  G,  aorta;  H ,  arch  of  the  aorta ;  K,  innominate  artery ; 
L,  right  common  carotid  artery;  M,  right  subclavian  artery;  N,  thyroid  cartilage 
forming  upper  portion  of  the  larynx ;  O,  trachea. 

smaller  branches,  called  bronchial  tubes.  These  divide  into 
smaller  tubes,  which  continue  subdividing  till  the  whole  lung 
is  penetrated  by  the  branches,  the  extremities  of  which  are 
extremely  minute.  To  all  these  branches  the  general  name  of 
bronchial  tubes  is  given.  The  smallest  are  only  about  one- 
fiftieth  of  an  inch  in  diameter. 


2O6 


PRACTICAL  PHYSIOLOGY. 


Now  the  walls  of  the  windpipe,  and  of  the  larger  bronchial 
tubes  would  readily  collapse,  and  close  the  passage  for  air, 
but  for  a  wise  precaution.  The  horseshoe-shaped  rings  of  car- 
tilage in  the  trachea  and  the  plates  of  cartilage  in  the  bronchial 
tubes  keep  these  passages  open.  Again,  these  air  passages  have 
elastic  fibers  running  the  length  of  the  tubes,  which  allow  them 
to  stretch  and  bend  readily  with  the  movements  of  the  neck. 

205.  The  Cilia  of  the  Air  Passages.     The  inner  surfaces 
of  the  windpipe   and  bronchial  tubes  are  lined  with  mucous 

membrane,  continuous  with  that  of 
the  throat,  the  mouth,  and  the  nostrils, 
the  secretion  from  which  serves  to 
keep  the  parts  moist. 

Delicate,  hair-like  filaments,  not  un- 
like the  pile  on  velvet,  called  cilia, 
spring  from  the  epithelial  lining  of 
the  air  tubes.  Their  constant  wavy 
movement  is  always  upwards  and  out- 
wards, towards  the  mouth.  Thus  any 
excessive  secretion,  as  of  bronchitis 
or  catarrh,  is  carried  upwards,  and 
finally  expelled  by  coughing.  In  this 
way,  the  lungs  are  kept  quite  free 

'its  Divisions  and"subdiAdsion7.  from  particles  of  foreign  matter  de- 
(Showing  groups  of  air  cells  at  rived  from  the   air.      Otherwise  we 

the  termination  of  minute  bron-      fa      M       ff        and     ft        be  j     d 
chial  tubes.) 

from  the  accumulation  of  mucus  and 

dust  in  the  air  passages.     Thus  these  tiny  cilia  act  as  dusters 
which  Nature  uses  to  keep  the  air  tubes  free  and  clean  (Fig.  5). 

206.  The  Lungs.      The  lungs,  the  organs  of  respiration, 
are  two  pinkish  gray  structures  of  a  light,  spongy  appearance, 
that  fill  the  chest  cavity,  except  the  space  taken  up  by  the 
heart    and    large    vessels.       Between  the    lungs    are    situated 


FIG.  87.— Bronchial  tube,  with 


RESPIRATION. 


2O7 


the  large  bronchi,  the  oesophagus,  the  heart  in  its  pericardium, 
and  the  great  blood-vessels.  The  base  of  the  lungs  rests  on 
the  dome-like  diaphragm,  which  separates  the  chest  from  the 
abdomen.  This  partly  muscular  and  partly  tendinous  partition 
is  a  most  important 
factor  in  breathing. 

Each  lung  is 
covered,  except  at 
one  point,  with  an 
elastic  serous  mem- 
brane in  a  double 
layer,  called  the 
pleura.  One  layer 
closely  envelops  the 
lung,  at  the  apex  of 
which  it  is  reflected 
to  the  wall  of  the 
chest  cavity  of  its 
own  side,  which  it 
lines.  The  two  layers 
thus  form  between 
them  a  closed  sac,  a 
serous  cavity  (see 
Fig.  69,  also  note, 
p.  176). 

In  health  the  two 
pleural  surfaces  of  the  lungs  are  always  in  contact,  and  they 
secrete  just  enough  serous  fluid  to  allow  the  surfaces  to  glide 
smoothly  upon  each  other.  Inflammation  of  this  membrane  is 
called  pleurisy.  In  this  disease  the  breathing  becomes  very 
painful,  as  the  secretion  of  glairy  serum  is  suspended,  and  the 
dry  and  inflamed  surfaces  rub  harshly  upon  each  other. 

The  root  of  the  lung,  as  it  is  called,  is  formed  by  the  bronchi, 
two  pulmonary  arteries,  and  two  pulmonary  veins.    The  nerves 


FIG.  88. —The  Lungs  with  the  Trachea,  Bronchi,  and 
Larger  Bronchial  Tubes  exposed.    (Posterior  view.) 

A,  division  of  left  bronchus  to  upper  lobe ;  B,  left  branch 
of  the  pulmonary  artery ;  C,  left  bronchus ;  D,  left  superior 
pulmonary  vein  ;  E,  left  inferior  pulmonary  vein  ;  F,  left 
auricle ;  K,  inferior  vena  cava ;  L,  division  of  right  bronchus 
to  lower  lobe;  M,  right  inferior  pulmonary  vein  ;  N,  right 
superior  pulmonary  vein  ;  O,  right  branch  of  the  pulmon- 
ary artery ;  P,  division  of  right  bronchus  to  upper  lobe  ; 
R,  left  ventricle  ;  S,  right  ventricle. 


208 


PRACTICAL    PHYSIOLOGY. 


and  lymphatic  vessels  of  the  lung  also  enter  at  the  root.  If  we 
only  remember  that  all  the  bronchial  tubes,  great  and  small, 
are  hollow,  we  may  compare  the  whole  system  to  a  short  bush  or 
tree  growing  upside  down  in  the  chest,  of  which  the  trachea  is 
the  trunk,  and  the  bronchial  tubes  the  branches  of  various  sizes. 

207.  Minute  Structure  of  the  Lungs.  If  one  of  the  small- 
est bronchial  tubes  be  traced  in  its  tree-like  ramifications,  it 
will  be  found  to  end  in  an  irregular  funnel-shaped  passage  wider 
than  itself.  Around  this  passage  are  grouped  a  number  of 
honeycomb-like  sacs,  the  air  cells1  or  alveoli  of  the  lungs. 
These  communicate  freely  with  the  passage,  and  through  it  with 
the  bronchial  branches,  but  have  no  other  openings.  The  whole 


FIG.  89. 
A,  diagrammatic  representation  of  the  ending  of  a  bronchial  tube  in  air  sacs  or  alveoli; 

B,  termination  of  two  bronchial  tubes  in  enlargement  beset  with  air  sacs  (Huxley); 

C,  diagrammatic  view  of  an  air  sac.     a  lies  within  sac  and  points  to  epithelium 
lining  wall ;    b,  partition   between   two  adjacent  sacs,  in  which  run   capillaries ; 
c,  elastic  connective  tissue  (Huxley). 

arrangement  of  passages  and  air  cells  springing  from  the  end 
of  a  bronchial  tube,  is  called  an  ultimate  lobule.  Now  each 
lobule  is  a  very  small  miniature  of  a  whole  lung,  for  by  the 
grouping  together  of  these  lobules  another  set  of  larger  lobules 
is  formed. 


1  The  word  "  cell  "  is  not  used  in  this  connection  in  its  technical  signification  of  a 
histological  unit  of  the  body  (sec.  12),  but  merely  in  its  primary  sense  of  a  small  cavity. 


RESPIRATION. 


209 


In  like  manner  countless  numbers  of  these  lobules,  bound 
together  by  connective  tissue,  are  grouped  after  the  same  fashion 
to  form  by  their  aggregation  the  lobes  of  the  lung.  The  right 
lung  has  three  such  lobes;  and  the  left,  two.  Each  lobule  has  a 


Maximum  inspiration 


Complonental  air 


Ordinary   inspiration 

TIDAL  AIR 

Ordinary  expiration 


Supplemental   air 
Maximum  expiration 

Residual  air    — 


y   Vital  capacity 


Capacity  of  equilibrium 


FIG.  90. —  Diagram  to  illustrate  the  Amounts  of  Air  contained  by  the  Lungs  in 
Various  Phases  of  Ordinary  and  of  Forced  Respiration. 


branch  of  the  pulmonary  artery  entering  it,  and  a  similar  rootlet 
of  the  pulmonary  vein  leaving  it.  It  also  receives  lymphatic 
vessels,  and  minute  twigs  of  the  pulmonary  plexus  of  nerves. 

The  walls  of  the  air  cells  are  of  extreme  thinness,  consisting 
of  delicate  elastic  and  connective  tissue,  and  lined  inside  by  a 
single  layer  of  thin  epithelial  cells.  In  the  connective  tissue 
run  capillary  vessels  belonging  to  the  pulmonary  artery  and  veins. 
Now  these  delicate  vessels  running  in  the  connective  tissue  are 
surrounded  on  all  sides  by  air  cells.  It  is  evident,  then,  that  the 
blood  flowing  through  these  capillaries  is  separated  from  the 
air  within  the  cells  only  by  the  thin  walls  of  the  vessels,  and 
the  delicate  tissues  of  the  air  cells. 


2IO  PRACTICAL    PHYSIOLOGY. 

This  arrangement  is  perfectly  adapted  for  an  interchange 
between  the  blood  in  the  capillaries  and  the  air  in  the  air  cells. 
This  will  be  more  fully  explained  in  sec.  214. 

208.  Capacity  of  the  Lungs.  In  breathing  we  alternately  take 
into  and  expel  from  the  lungs  a  certain  quantity  of  air.  With  each 
quiet  inspiration  about  30  cubic  inches  of  air  enter  the  lungs,  and  30 
cubic  inches  pass  out  with  each  expiration.  The  air  thus  passing  into 
and  out  of  the  lungs  is  called  tidal  air.  After  an  ordinary  inspira- 
tion, the  lungs  contain  about  230  cubic  inches  of  air.  By  taking  a 
deep  inspiration,  about  100  cubic  inches  more  can  be  taken  in.  This 
extra  amount  is  called  complemental  air. 

After  an  ordinary  expiration,  about  200  cubic  inches  are  left  in 
the  lungs,  but  by  forced  expiration  about  one-half  of  this  may  be 
driven  out.  This  is  known  as  supplemental  air.  The  lungs  can 
never  be  entirely  emptied  of  air,  about  75  to  100  cubic  inches  always 
remaining.  This  is  known  as  the  residual  air. 

The  air  that  the  lungs  of  an  adult  man  are  capable  of  containing 
is  thus  composed  : 

Complemental  air 100  cubic  inches. 

Tidal  " 30      " 

Supplemental     " 100      "  " 

Residual  "  .  100      "          " 


Total  capacity  of  lungs    ......     330      "  " 

If,  then,   a   person   proceeds,  after  taking  the  deepest  possible 
breath,  to  breath  out  as  much  as  he  can,  he  expels  : 

Complemental  air 100  cubic  inches. 

Tidal  " 30       "          " 

Supplemental     " 100       "          " 


230 

This  total  of  230  cubic  inches  forms  what  is  called  the  vital 
capacity  of  the  chest  (Fig.  90). 


RESPIRATION.  211 

209.  The  Movements  of  Breathing.     The  act  of  breathing 
consists  of  a  series  of  rhythmical  movements,  succeeding  one 
another  in  regular  order.     In  the  first  movement,  inspiration, 
the  chest  rises,  and  there  is  an  inrush  of  fresh  air  ;  this  is  at 
once  followed  by  expiration,  the  falling  of  the  chest  walls,  and 
the  output  of  air.     A  pause  now  occurs,  and  the  same  breath- 
ing movements  are  repeated. 

The  entrance  and  the  exit  of  air  into  the  respiratory  passages 
are  accompanied  with  peculiar  sounds  which  are  readily  heard 
on  placing  the  ear  at  the  chest  wall.  These  sounds  are  greatly 
modified  in  various  pulmonary  diseases,  and  hence  are  of  great 
value  to  the  physician  in  making  a  correct  diagnosis. 

In  a  healthy  adult,  the  number  of  respirations  should  be  from 
1 6  to  18  per  minute,  but  they  vary  with  age,  that  of  a  newly 
born  child  being  44  for  the  same  time.  Exercise  increases  the 
number,  while  rest  diminishes  it.  In  standing,  the  rate  is 
more  than  when  lying  at  rest.  Mental  emotion  and  excitement 
quicken  the  rate.  The  number  is  smallest  during  sleep.  Dis- 
ease has  a  notable  effect  upon  the  frequency  of  respirations. 
In  diseases  involving  the  lungs,  bronchial  tubes,  and  the  pleura, 
the  rate  may  be  alarmingly  increased,  and  the  pulse  is  quick- 
ened in  proportion. 

210.  The  Mechanism  of  Breathing.     The  chest  is  a  cham- 
ber with   bony  walls,  the  ribs  connecting   in   front  with  the 
breastbone,  and  behind  with  the  spine.     The  spaces  between 
the  ribs  are  occupied  by  the  intercostal  muscles,  while  large 
muscles  clothe  the  entire  chest.     The  diaphragm  serves  as  a 
movable  floor  to  the  chest,  which  is  an  air-tight  chamber  with 
movable  walls  and  floor.     In  this  chamber  are  suspended  the 
lungs,  the   air  cells  of   which    communicate  with   the  outside 
through  the  bronchial  passages,  but  have  no  connection  with 
the  chest  cavity.     The  thin  space  between  the  lungs  and  the 
rib  walls,  called  the  pleural  cavity,  is  in  health  a  vacuum. 


212 


PRACTICAL    PHYSIOLOGY. 


Now,  when  the  diaphragm  contracts,  it  descends  and  thus 
increases  the  depth  of  the  chest  cavity.  A  quantity  of  air  is 
now  drawn  into  the  lungs  and  causes  them  to  expand,  thus 
filling  up  the  increased  space.  As  soon  as  the  diaphragm  re- 
laxes, returning  to  its  arched  position  and 
reducing  the  size  of  the  chest  cavity,  the 
air  is  driven  from  the  lungs,  which  then 
diminish  in  size.  After  a  short  pause, 
the  diaphragm  again  contracts,  and  the 
same  round  of  operation  is  constantly 
repeated. 

The  walls  of  the  chest  being  movable, 
by  the  contractions  of  the  intercostals 
and  other  muscles,  the  ribs  are  raised 
and  the  breastbone  pushed  forward. 
The  chest  cavity  is  thus  enlarged  from 
side  to  side  and  from  behind  forwards. 
Thus,  by  the  simultaneous  descent  of 
the  diaphragm  and  the  elevation  of  the 
ribs,  the  cavity  of  the  chest  is  increased 

in  three  directions,  —  downwards,  side- 
FiG.9i.-DiagrammaticSec-  ^  forwardg 

tion  of  the  Trunk.  (Show-          *   ' 

ing  the  expansion  of  the  It  is  thus  evident  that  inspiration  is  due 
chest  and  the  movement  of  to  a  series  of  muscular  contractions. 

the  ribs   by  action   of  the  .,  ,•  -u 

lungs.)  [The  dotted  lines  As  soon  as  the  contractions  cease,  the 
indicate  the  position  dur-  elastic  lung  tissue  resumes  its  original 
ing  inspiration.]  position,  just  as  an  extended  rubber 

band  recovers  itself.     As  a  result,  the  original  size  of  the  chest 

cavity  is  restored,  and  the  inhaled  air  is  driven  from  the  lungs. 

Expiration  may  then  be  regarded  as  the  result  of  an  elastic 

recoil,  arid  not  of  active  muscular  contractions. 

211.  Varieties  of  Breathing.  This  is  the  mechanism  of 
quiet,  normal  respiration.  When  the  respiration  is  difficult, 
additional  forces  are  brought  into  play.  Thus  when  the  wind- 


RESPIRATION.  2  I  3 

pipe  and  bronchial  tubes  are  obstructed,  as  in  croup,  asthma, 
or  consumption,  many  additional  muscles  are  made  use  of  to 
help  the  lungs  to  expand.  The  position  which  asthmatics  often 
assume,  with  arms  raised  to  grasp  something  for  support,  is 
from  the  need  of  the  sufferer  to  get  a  fixed  point  from  which 
the  muscles  of  the  arm  and  chest  may  act  forcibly  in  raising 
the  ribs,  and  thus  securing  more  comfortable  breathing. 

The  visible  movements  of  breathing  vary  according  to  cir- 
cumstances. In  infants  the  action  of  the  diaphragm  is  marked, 
and  the  movements  of  the  abdomen  are  especially  obvious. 
This  is  called  abdominal  breathing.  In  women  the  action  of 
the  ribs  as  they  rise  and  fall,  is  emphasized  more  than  in  men, 
and  this  we  call  costal  breathing.  In  young  persons  and  in 
men,  the  respiration  not  usually  being  impeded  by  tight  cloth- 
ing, the  breathing  is  normal,  being  deep  and  abdominal. 

Disease  has  a  marked  effect  upon  the  mode  of  breathing. 
Thus,  when  children  suffer  from  some  serious  chest  disease, 
the  increased  movements  of  the  abdominal  walls  seem  distress- 
ing. So  in  fracture  of  the  ribs,  the  surgeon  envelops  the 
overlying  part  of  the  chest  with  long  strips  of  firm  adhesive 
plaster  to  restrain  the  motions  of  chest  respiration,  that  they 
may  not  disturb  the  jagged  ends  of  the  broken  bones.  Again, 
in  painful  diseases  of  the  abdomen,  the  sufferer  instinctively 
suspends  the  abdominal  action  and  relies  upon  the  chest 
breathing.  These  deviations  from  the  natural  movements  of 
respiration  are  useful  to  the  physician  in  ascertaining  the  seat 
of  disease. 

212.  The  Nervous  Control  of  Respiration.  It  is  a  matter 
of  common  experience  that  one's  breath  may  be  held  for  a 
short  time,  but  the  need  of  fresh  air  speedily  gets  the  mastery, 
and  a  long,  deep  breath  is  drawn.  Hence  the  efforts  of  crim- 
inals to  commit  suicide  by  persistent  restraint  of  their  breath- 
ing, are  always  a  failure.  At  the  very  worst,  unconsciousness 
ensues,  and  then  respiration  is  automatically  resumed.  Thus 


214  PRACTICAL  PHYSIOLOGY. 

a  wise  Providence  defeats  the  purpose  of  crime.  The  move- 
ments of  breathing  go  on  without  our  attention.  In  sleep  the 
regularity  of  respiration  is  even  greater  than  when  awake. 
There  is  a  particular  part  of  the  nervous  system  that  presides 
over  the  breathing  function.  It  is  situated  in  that  part  of  the 
brain  called  the  medulla  oblongata,  and  is  fancifully  called  the 
"vital  knot"  (sec.  270).  It  is  injury  to  this  respiratory  center 
which  proves  fatal  in  cases  of  broken  neck. 

From  this  nerve  center  there  is  sent  out  to  the  nerves  that 
supply  the  diaphragm  and  other  muscles  of  breathing,  a  force 
which  stimulates  them  to  regular  contraction.  This  breathing 
center  is  affected  by  the  condition  of  the  blood.  It  is  stimu- 
lated by  an  excess  of  carbon  dioxid  in  the  blood,  and  is  quieted 
by  the  presence  of  oxygen. 

Experiment  108.  To  locate  the  lungs.  Mark  out  the  boundaries  of  the 
lungs  by  "  sounding  "  them  ;  that  is,  by  percussion,  as  it  is  called.  This 
means  to  put  the  forefinger  of  the  left  hand  across  the  chest  or  back, 
and  to  give  it  a  quick,  sharp  rap  with  two  or  three  fingers.  Note  where 
it  sounds  hollow,  resonant.  This  experiment  can  be  done  by  the  student 
with  only  imperfect  success,  until  practice  brings  some  skill. 

Experiment  109.  Borrow  a  stethoscope,  and  listen  to  the  respiration 
over  the  chest  on  the  right  side.  This  is  known  as  auscultation.  Note  the 
difference  of  the  sounds  in  inspiration  and  in  expiration.  Do  not  confuse 
the  heart  sounds  with  those  of  respiration.  The  respiratory  murmurs  may  be 
heard  fairly  well  by  applying  the  ear  flat  to  the  chest,  with  only  one  garment 
interposed. 

Experiment  no.  Get  a  sheep's  lungs,  with  the  windpipe  attached. 
Ask  for  the  heart  and  lungs  all  in  one  mass.  Take  pains  to  examine  the 
specimen  first,  and  accept  only  a  good  one.  Parts  are  apt  to  be  hastily 
snipped  or  mangled.  Examine  the  windpipe.  Note  the  horseshoe-shaped 
rings  of  cartilage  in  front,  which  serve  to  keep  it  open. 

Experiment  in.  Examine  one  bronchus,  carefully  dissecting  away  the 
lung  tissue  with  curved  scissors.  Follow  along  until  small  branches  of  the 
bronchial  tubes  are  reached.  Take  time  for  the  dissection,  and  save  the 
specimen  in  dilute  alcohol.  Put  pieces  of  the  lung  tissue  in  a  basin  of 
water,  and  note  that  they  float. 


RESPIRATION.  2  I  5 

The  labored  breathing  of  suffocation  and  of  lung  diseases  is 
due  to  the  excessive  stimulation  of  this  center,  caused  by  the 
excess  of  carbon  dioxid  in  the  blood.  Various  mental  influ- 
ences from  the  brain  itself,  as  the  emotions  of  alarm  or  joy  or 
distress,  modify  the  action  of  the  respiratory  center. 

Again,  nerves  of  sensation  on  the  surface  of  the  body  convey 
influences  to  this  nerve  center  and  lead  to  its  stimulation,  re- 
sulting in  a  vigorous  breathing  movement.  Thus  a  dash  of 
cold  water  on  the  face  or  neck  of  a  fainting  person  instantly 
produces  a  deep,  long-drawn  breath.  Certain  drugs,  as  opium, 
act  to  reduce  the  activity  of  this  nerve  center.  Hence,  in 
opium  poisoning,  special  attention  should  be  paid  to  keeping 
up  the  respiration.  The  condition  of  the  lungs  themselves  is 
made  known  to  the  breathing  center,  by  messages  sent  along 
the  branches  of  the  great  pneumogastric  nerve  (page  276), 
leading  from  the  lungs  to  the  medulla  oblongata. 

213.  Effects  of  Respiration  upon  the  Blood.  The  blood 
contains  three  gases,  partly  dissolved  in  it  and  partly  in  chem- 
ical union  with  certain  of  its  constituents.  These  are  oxygen, 
carbon  dioxid,  and  nitrogen.  The  latter  need  not  be  taken 
into  account.  The  oxygen  is  the  nourishing  material  which 
the  tissues  require  to  carry  on  their  work.  The  carbon  dioxid 
is  a  waste  substance  which  the  tissues  produce  by  their  activity, 
and  which  the  blood  carries  away  from  them. 

As  before  shown,  the  blood  as  it  flows  through  the  tissues 
loses  most  of  its  oxygen,  and  carbon  dioxid  takes  its  place. 
Now  if  the  blood  is  to  maintain  its  efficiency  in  this  respect,  it 
must  always  be  receiving  new  supplies  of  oxygen,  and  also  have 
some  mode  of  throwing  off  its  excess  of  carbon  dioxid.  This, 
then,  is  the  double  function  of  the  process  of  respiration. 
Again,  the  blood  sent  out  from  the  left  side  of  the  heart  is  of 
a  bright  scarlet  color.  After  its  work  is  done,  and  the  blood 
returns  to  the  right  side  of  the  heart,  it  is  of  a  dark  purple 


2l6  PRACTICAL    PHYSIOLOGY. 

color.  This  change  in  color  takes  place  in  the  capillaries,  and 
is  due  to  the  fact  that  there  the  blood  gives  up  most  of  its 
oxygen  to  the  tissues  and  receives  from  them  a  great  deal  of 
carbon  dioxid. 

In  brief,  while  passing  through  the  capillaries  of  the  lungs  the 
blood  has  been  changed  from  the  venous  to  the  arterial  blood. 
That  is  to  say,  the  blood  in  its  progress  through  the  lungs  has 
rid  itself  of  its  excess  of  carbon  dioxid  and  obtained  a  fresh 
supply  of  oxygen.1 

214.  Effects  of  Respiration  upon  the  Air  in  the  Lungs. 
It  is  well  known  that  if  two  different  liquids  be  placed  in  a 
vessel  in  contact  with  each  other  and  left  undisturbed,  they 
do  not  remain  separate,  but  gradually  mix,  and  in  time  will  be 
perfectly  combined.  This  is  called  diffusion  of  liquids.  The 
same  thing  occurs  with  gases,  though  the  process  is  not  visible. 
This  is  known  as  the  diffusion  of  gases.  It  is  also  true  that 
two  liquids  will  mingle  when  separated  from  each  other  by  a 
membrane  (sec.  129).  In  a  similar  manner  two  gases,  espe- 
cially if  of  different  densities,  may  mingle  even  when  separated 
from  each  other  by  a  membrane. 

In  a  general  way  this  explains  the  respiratory  changes 
that  occur  in  the  blood  in  the  lungs.  Blood  containing  oxygen 
and  carbon  dioxid  is  flowing  in  countless  tiny  streams  through 
the  walls  of  the  air  cells  of  the  lungs.  The  air  cells  themselves 
contain  a  mixture  of  the  same  two  gases.  A  thin,  moist 
membrane,  well  adapted  to  allow  gaseous  diffusion,  separates 
the  blood  from  the  air.  This  membrane  is  the  delicate  wall 
of  the  capillaries  and  the  epithelium  of  the  air  cells.  By 

1  "  The  student  must  guard  himself  against  the  idea  that  arterial  blood  contains 
no  carbonic  acid,  and  venous  blood  no  oxygen.  In  passing  through  the  lungs 
venous  blood  loses  only  a  part  of  its  carbonic  acid  ;  and  arterial  blood,  in  passing 
through  the  tissues,  loses  only  a  part  of  its  oxygen.  In  blood,  however  venous,  there 
is  in  health  always  some  oxygen ;  and  in  even  the  brightest  arterial  blood  there  is 
actually  more  carbonic  acid  than  oxygen."  —  T.  H.  HUXLEY. 


RESPIRATION. 


217 


experiment  it  has  been  found  that  the  pressure  of  oxygen  in 
the  blood  is  less  than  that  in  the  air  cells,  and  that  the  pressure 
of  carbon  dioxid  gas  in  the  blood  is  greater  than  that  in  the 
air  cells.  As  a  result,  a  diffusion  of  gases  ensues.  The  blood 
gains  oxygen  and  loses 
carbon  dioxid,  while  the 
air  cells  lose  oxygen  and 
gain  the  latter  gas. 

The  blood  thus  be- 
comes purified  and  re- 
invigorated,  and  at  the 
same  time  is  changed  in 
color  from  purple  to 
scarlet,  from  venous  to 
arterial.  It  is  now  evident 
that  if  this  interchange 

is    tO   Continue,  the   air   in       A,  small  branch  of  pulmonary  artery  ;    B,  twigs  of 

pulmonary  artery  anastomosing  to  form  peripheral 
network  of  the  primitive  air  cells  ;  C,  capillary  net- 
work around  the  walls  of  the  air  sacs ;  D,  branches 
of  network  converging  to  form  the  veinlets  of  the 
pulmonary  veins. 


FIG.  92.  —  Capillary  Network  of  the  Air  Cells 
and  Origin  of  the  Pulmonary  Veins. 


the  cells  must  be  con- 
stantly renewed,  its  oxy- 
gen restored,  and  its 
excess  of  carbon  dioxid 
removed.  Otherwise  the  process  just  described  would  be 
reversed,  making  the  blood  still  more  unfit  to  nourish  the 
tissues,  and  more  poisonous  to  them  than  before. 

215.  Change  in  the  Air  in  Breathing.  The  air  which  we  exhale 
during  respiration  differs  in  several  important  particulars  from  the 
air  we  inhale.  Both  contain  chiefly  the  three  gases,  though  in  differ- 
ent quantities,  as  the  following  table  shows. 


Inspired  air  contains 
Expired  air  contains 


Oxygen. 
20.81 
16.03 


Nitrogen. 

79-15 

79-58 


Carbon  dioxid. 

.04  - 
4-38 


That  is,  expired  air  contains  about  five  per  cent  less  oxygen  and 
five  per  cent  more  carbon  dioxid  than  inspired  air. 


2l8  PRACTICAL    PHYSIOLOGY. 

The  temperature  of  expired  air  is  variable,  but  generally  is  higher 
than  that  of  inspired  air,  it  having  been  in  contact  with  the  warm  air 
passages.  It  is  also  loaded  with  aqueous  vapor,  imparted  to  it  like 
the  heat,  not  in  the  depth  of  the  lungs,  but  in  the  upper  air 
passages. 

Expired  air  contains,  besides  carbon  dioxid,  various  impurities, 
many  of  an  unknown  nature,  and  all  in  small  amounts.  When  the 
expired  air  is  condensed  in  a  cold  receiver,  the  aqueous  product  is 
found  to  contain  organic  matter,  which,  from  the  presence  of  micro- 
orgaAisms,  introduced  in  the  inspired  air,  is  apt  to  putrefy  rapidly. 
Some  of  these  organic  substances  are  probably  poisonous,  either  so 
in  themselves,  as  produced  in  some  manner  in  the  breathing  appara- 
tus, or  poisonous  as  being  the  products  of  decomposition.  For  it  is 
known  that  various  animal  substances  give  rise,  by  decomposition,  to 
distinct  poisonous  products  known  as  ptomaines.  It  is  possible 
that  some  of  the  constituents  of  the  expired  air  are  of  an  allied 
nature.  See  under  «  Bacteria  "  (Chapter  XIV). 

At  all  events,  these  substances  have  an  injurious  action,  for  an 
atmosphere  containing  simply  one  per  cent  of  pure  carbon  dioxid  has 
very  little  hurtful  effect  on  the  animal  economy,  but  an  atmosphere  in 
which  the  carbon  dioxid  has  been  raised  one  per  cent  by  breathing  is 
highly  injurious. 

The  quantity  of  oxygen  removed  from  the  air  by  the  breathing  of 
an  adult  person  at  rest  amounts  daily  to  about  1 8  cubic  feet.  About 
the  same  amount  of  carbon  dioxid  is  expelled,  and  this  could  be  repre- 
sented by  a  piece  of  pure  charcoal  weighing  9  ounces.  The  quantity 
of  carbon  dioxid,  however,  varies  with  the  age,  and  is  increased  also 
by  external  cold  and  by  exercise,  and  is  affected  by  the  kind  of  food. 
The  amount  of  water,  exhaled  as  vapor,  varies  from  6  to  20  ounces 
daily.  The  average  daily  quantity  is  about  one-half  a  pint. 

216.  Modified  Respiratory  Movements.  The  respiratory 
column  of  air  is  often  used  in  a  mechanical  way  to  expel  bodies 
from  the  upper  air  passages.  There  are  also,  in  order  to 
secure  special  ends,  a  number  of  modified  movements  not  dis- 
tinctly respiratory.  The  following  peculiar  respiratory  acts  call 
for  a  few  words  of  explanation. 


RESPIRATION. 


2I9 


A  sigh  is  a  rapid  and  generally  audible  expiration,  due  to 
the  elastic  recoil  of  the  lungs  and  chest  walls.  It  is  often 
caused  by  depressing  emotions.  Yawning  is  a  deep  inspira- 
tion with  a  stretching  of  the  muscles  of  the  face  and  mouth, 
and  is  usually  excited  by  fatigue  or  drowsiness,  but  often  occurs 
from  a  sort  of  contagion. 

Hiccough  is  a  sudden  jerking  inspiration  due  to  the  spas- 
modic contraction  of  the  diaphragm  and  of  the  glottis,  caus- 
ing the  air  to  rush  suddenly  through  the  larynx,  and  produce 
this  peculiar  sound.  Snoring  is  caused  by  vibration  of  the  soft 
palate  during  sleep,  and  is  habitual  with  some,  although  it  occurs 
with  many  when  the  system  is  unusually  exhausted  and  relaxed. 

Laughing  consists  of  a  series  of  short,  rapid,  spasmodic 
expirations  which  cause  the  peculiar  sounds,  with  characteristic 
movements  of  the  facial  muscles.  Crying,  caused  by  emotional 
states,  consists  of  sudden  jerky  expirations  with  long  inspira- 
tions, with  facial  movements  indicative  of  distress.  In  sobbing, 
which  often  follows  long-continued  crying,  there  is  a  rapid 
series  of  convulsive  inspirations,  with  sudden  involuntary  con- 
tractions of  the  diaphragm.  Laughter,  and  sometimes  sobbing, 
like  yawning,  may  be  the  result  of  involuntary  imitation. 


Experiment  112.  Simple  Apparatus  to  Illustrate  the  Movements  of  the 
Lungs  in  the  Chest.  —  T  is  a  bottle  from 
which  the  bottom  has  been  removed ;  D,  a 
flexible  and  elastic  membrane  tied  on  the 
bottle,  and  capable  of  being  pulled  out  by 
the  string  S,  so  as  to  increase  the  capacity 
of  the  bottle.  L  is  a  thin  elastic  bag  repre- 
senting the  lungs.  It  communicates  with 
the  external  air  by  a  glass  tube  fitted  air- 
tight through  a  cork  in  the  neck  of  the 
bottle.  \Vhen  D  is  drawn  down,  the  pres- 
sure of  the  external  air  causes  L  to  expand. 
When  the  string  is  let  go,  L  contracts 
again,  by  virtue  of  its  elasticity.  FIG.  93. 


22O  PRACTICAL    PHYSIOLOGY. 

Coughing  is  produced  by  irritation  in  the  upper  part  of  the 
windpipe  and  larynx.  A  deep  breath  is  drawn,  the  opening 
of  the  windpipe  is  closed,  and  immediately  is  burst  open  with 
a  violent  effort  which  sends  a  blast  of  air  through  the  upper 
air  passages.  The  object  is  to  dislodge  and  expel  any  mucus 
or  foreign  matter  that  is  irritating  the  air  passages. 

Sneezing  is  like  coughing ;  the  tongue  is  raised  against  the 
soft  palate,  so  the  air  is  forced  through  the  nasal  passages.  It 
is  caused  by  an  irritation  of  the  nostrils  or  eyes.  In  the  begin- 
ning of  a  cold  in  the  head,  for  instance,  the  cold  air  irritates 
the  inflamed  mucous  membrane  of  the  nose,  and  causes 
repeated  attacks  of  sneezing. 

217.   How  the  Atmosphere  is  Made  Impure.     The  air 

around  us  is  constantly  being  made  impure  in  a  great  variety 
of  ways.  The  combustion  of  fuel,  the  respiration  of  men  and 
animals,  the  exhalations  from  their  bodies,  the  noxious  gases 
and  effluvia  of  the  various  industries,  together  with  the  changes 
of  fermentation  and  decomposition  to  which  all  organized 
matter  is  liable,  —  all  tend  to  pollute  the  atmosphere. 

The  necessity  of  external  ventilation  has  been  foreseen  for 
us.  The  forces  of  nature,  —  the  winds,  sunlight,  rain,  and 
growing  vegetation,  —  all  of  great  power  and  universal  distri- 
bution and  application,  restore  the  balance,  and  purify  the  air. 
As  to  the  principal  gases,  the  air  of  the  city  does  not  differ 
materially  from  that  of  rural  sections.  There  is,  however,  a 
vastly  greater  quantity  of  dust  and  smoke  in  the  air  of  towns. 
The  breathing  of  this  dust,  to  a  greater  or  less  extent  laden 
with  bacteria,  fungi,  and  the  germs  of  disease,  is  an  ever-present 
and  most  potent  menace  to  public  and  personal  health.  It  is 
one  of  the  main  causes  of  the  excess  of  mortality  in  towns  and 
cities  over  that  of  country  districts. 

This  is  best  shown  in  the  overcrowded  streets  and  houses  of 
great  cities,  which  are  deprived  of  the  purifying  influence  of 


RESPIRATION.  221 

sun  and  air.  The  fatal  effect  of  living  in  vitiated  air  is  espe- 
cially marked  in  the  mortality  among  infants  and  children 
living  in  the  squalid  and  overcrowded  sections  of  our  great 
cities.  The  salutary  effect  of  sunshine  is  shown  by  the  fact 
that  mortality  is  usually  greater  on  the  shady  side  of  the  street. 

218.   How  the  Air  is  Made  Impure  by  Breathing.     It  is 

not  the  carbon  dioxid  alone  that  causes  injurious  results  to 
health,  it  is  more  especially  the  organic  matter  thrown  off 
in  the  expired  air.  The  carbon  dioxid  which  accompanies  the 
organic  matter  is  only  the  index.  In  testing  the  purity  of  air 
it  is  not  difficult  to  ascertain  the  amount  of  carbon  dioxid 
present,  but  it  is  no  easy  problem  to  measure  the  amount  of 
organic  matter.  Hence  it  is  the  former  that  is  looked  for  in 
factories,  churches,  schoolrooms,  and  when  it  is  found  to  exceed 
.07  per  cent  it  is  known  that  there  is  a  hurtful  amount  of  organic 
matter  present. 

The  air  as  expelled  from  the  lungs  contains,  not  only  a  cer- 
tain amount  of  organic  matter  in  the  form  of  vapor,  but  minute 
solid  particles  of  debris  and  bacterial  micro-organisms  (Chap. 
XIV).  The  air  thus  already  vitiated,  after  it  leaves  the  mouth, 
putrefies  very  rapidly.  It  is  at  once  absorbed  by  clothing, 
curtains,  carpets,  porous  walls,  and  by  many  other  objects.  It 
is  difficult  to  dislodge  these  enemies  of  health  even  by  free 
ventilation.  The  close  and  disagreeable  odor  of  a  filthy  or 
overcrowded  room  is  due  to  these  organic  exhalations  from 
the  lungs,  the  skin,  and  the  unclean  clothing  of  the  occupants. 

The  necessity  of  having  a  proper  supply  of  fresh  air  in  en- 
closed places,  and  the  need  of  removal  of  impure  air  are  thus 
evident.  If  a  man  were  shut  up  in  a  tightly  sealed  room  con- 
taining 425  cubic  feet  of  air,  he  would  be  found  dead  or  nearly 
so  at  the  end  of  twenty-four  hours.  Long  before  this  time  he 
would  have  suffered  from  nausea,  headache,  dizziness,  and 
other  proofs  of  blood-poisoning.  These  symptoms  are  often  felt 


222  PRACTICAL  PHYSIOLOGY. 

by  those  who  are  confined  for  an  hour  or  more  in  a  room  where 
the  atmosphere  has  been  polluted  by  a  crowd  of  people.  The 
unpleasant  effects  rapidly  disappear  on  breathing  fresh  air. 

219.  The  Effect  on  the  Health  of  Breathing  Foul  Air. 
People  are  often  compelled  to  remain  indoors  for  many  hours, 
day  after  day,   in    shops,   factories,   or    offices,   breathing    air 
perhaps  only  slightly  vitiated,  but  still  recognized  as  "  stuffy." 
Such  persons  often   suffer  from   ill   health.     The  exact  form 
of  the  disturbance  of  health  depends  much  upon  the  heredi- 
tary proclivity  and  physical  make-up  of  the  individual.     Loss 
of  appetite,   dull  headache,  fretfulness,  persistent  weariness, 
despondency,  followed  by  a  general  weakness  and  an  impover- 
ished state  of  blood,  often  result. 

Persons  in  this  lowered  state  of  health  are  much  more  prone 
to  suffer  from  colds,  catarrhs,  bronchitis,  and  pneumonia  than 
if  they  were  living  in  the  open  air,  or  breathing  only  pure  air. 
Thus,  in  the  Crimean  War,  the  soldiers  who  lived  in  tents  in 
the  coldest  weather  were  far  more  free  from  colds  and  lung 
troubles  than  those  who  lived  in  tight  and  ill-ventilated  huts. 
In  the  early  fall  when  typhoid  fever  is  prevalent,  the  grounds 
of  large  hospitals  are  dotted  with  canvas  tents,  in  which  patients 
suffering  from  this  fever  do  much  better*  than  in  the  wards. 

This  tendency  to  inflammatory  diseases  of  the  air  passages 
is  aggravated  by  the  overheated  and  overdried  condition  of 
the  air  in  the  room  occupied.  This  may  result  from  burning 
gas,  from  overheated  furnaces  and  stoves,  hot-water  pipes,  and 
other  causes.  Serious  lung  diseases,  such  as  consumption,  are 
more  common  among  those  who  live  in  damp,  overcrowded,  or 
poorly  ventilated  homes. 

220.  The  Danger  from  Pulmonary  Infection.     The  germ 
of  pulmonary  consumption,  known  as  the  bacillus  tuberculosis, 
is  contained  in  the  breath  and  the  sputa  from  the  lungs  of  its 
victims.     It  is  not  difficult  to  understand  how  these  bacilli  may 


RESPIRATION.  223 

be  conveyed  through  the  air  from  the  lungs  of  the  sick  to  those 
of  apparently  healthy  people.  Such  persons  may,  however,  be 
predisposed,  either  constitutionally  or  by  defective  hygienic 
surroundings,  to  fall  victims  to  this  dreaded  disease.  Over- 
crowding, poor  ventilation,  and  dampness  all 
tend  to  increase  the  risk  of  pulmonary  in- 
fection. 

It  must  not  be  supposed  that  the  tubercle 
bacillus    is    necessarily   transmitted   directly  FIG.  94. 

through  the  air  from  the  lungs  of  the  sick  to   Example  of  a  Micro- 

i     •          IT  r     ,i_        i        1.1  Organism  —  Bacillus 

be  implanted  in  the  lungs   of   the    healthy.      Tubercuk)sis  in  Spu- 
The  germs  may  remain  for  a  time  in  the  dust      tum.        (Magnified 

_,  ,  ,  ,     ,        about  500  diameters.) 

and  debris  of  damp,  filthy,  and  overcrowded 
houses.    In  this  congenial  soil  they  retain  their  vitality  for  a  long 
time,  and  possibly  may  take  on  more  virulent  infective  properties 
than  they  possessed  when  expelled  from  the  diseased  lungs.1 

221.  Ventilation.  The  question  of  a  practicable  and  eco- 
nomical system  of  ventilation  for  our  homes,  schoolrooms, 
workshops,  and  public  places  presents  many  difficult  and  per- 
plexing problems.  It  is  perhaps  due  to  the  complex  nature  of 
the  subject,  that  ventilation,  as  an  ordinary  condition  of  daily 
health,  has  been  so  much  neglected.  The  matter  is  practically 
ignored  in  building  ordinary  houses.  The  continuous  renewal 
of  air  receives  little  if  any  consideration,  compared  with  the 
provision  made  to  furnish  our  homes  with  heat,  light,  and 

1  "  Consumption  is  a  disease  which  can  be  taken  from  others,  and  is  not  simply 
caused  by  colds.  A  cold  may  make  it  easier  to  take  the  disease.  It  is  usually  caused 
by  germs  which  enter  the  body  with  the  air  breathed.  The  matter  which  consump- 
tives cough  or  spit  up  contains  these  germs  in  great  numbers  —  frequently  millions 
are  discharged  in  a  single  day.  This  matter  spit  upon  the  floor,  wall,  or  elsewhere 
is  apt  to  dry,  become  pulverized,  and  float  in  the  air  as  dust.  The  dust  contains  the 
germs,  and  thus  they  enter  the  body  with  the  air  breathed.  The  breath  of  a  consump- 
tive does  not  contain  the  germs  and  will  not  produce  the  disease.  A  well  person 
catches  the  disease  from  a  consumptive  only  by  in  some  way  taking  in  the  matter 
coughed  up  by  the  consumptive."  —  Extract  from  a  circular  issued  by  the  Board  of 
Health  of  New  York  City. 


224  PRACTICAL  PHYSIOLOGY. 

water.  When  the  windows  are  closed  we  usually  depend  for 
ventilation  upon  mere  chance,  —  on  the  chimney,  the  fireplace, 
and  the  crevices  of  doors  and  windows.  The  proper  ventilation 
of  a  house  and  its  surroundings  should  form  as  prominent  a  con- 
sideration in  the  plans  of  builders  and  architects  as  do  the  grading 
of  the  land,  the  size  of  the  rooms,  and  the  cost  of  heating. 

The  object  of  ventilation  is  twofold  :  First,  to  provide  for 
the  removal  of  the  impure  air ;  second,  for  a  supply  of  pure 
air.  This  must  include  a  plan  to  provide  fresh  air  in  such  a 
manner  that  there  shall  be  no  draughts  or  exposure  of  the 
occupants  of  the  rooms  to  undue  temperature.  Hence,  what 
at  first  might  seem  an  easy  thing  to  do,  is,  in  fact,  one  of  the 
most  difficult  of  sanitary  problems. 

222.  Conditions  of  Efficient  Ventilation.  To  secure  proper 
ventilation  certain  conditions  must  be  observed.  The  pure  air 
introduced  should  not  be  far  below  the  temperature  of  the 
room,  or  if  so,  the  entering  current  should  be  introduced 
towards  the  ceiling,  that  it  may  mix  with  the  warm  air. 

Draughts  must  be  avoided.  If  the  circuit  from  entrance  to 
exit  is  short,  draughts  are  likely  to  be  produced,  and  impure 
air  has  less  chance  of  mixing  by  diffusion  with  the  pure  air. 
The  current  of  air  introduced  should  be  constant,  otherwise 
the  balance  may  occasionally  be  in  favor  of  vitiated  air.  If  a 
mode  of  ventilation  prove  successful,  it  should  not  be  interfered 
with  by  other  means  of  entrance.  Thus,  an  open  door  may 
prevent  the  incoming  air  from  passing  through  its  proper  chan- 
nels. It  is  desirable  that  the  inlet  be  so  arranged  that  it  can  be 
diminished  in  size  or  closed  altogether.  For  instance,  when 
the  outer  air  is  very  cold,  or  the  wind  blows  directly  into  the 
inlet,  the  amount  of  cold  air  entering  it  may  lower  the  tempera- 
ture of  the  room  to  an  undesirable  degree. 

In  brief,  it  is  necessary  to  have  a  thorough  mixing  of  pure 
and  impure  air,  so  that  the  combination  at  different  parts  of 


RESPIRATION.  225 

the  room  may  be  fairly  uniform.  To  secure  these  results, 
the  inlets  and  outlets  should  be  arranged  upon  principles  of 
ventilation  generally  accepted  by  authorities  on  public  health. 
It  seems  hardly  necessary  to  say  that  due  attention  must  be 
paid  to  the  source  from  which  the  introduced  air  is  drawn.  If 
it  be  taken  from  foul  cellars,  or  from  dirty  streets,  it  may  be  as 
impure  as  that  which  it  is  designed  to  replace. 

ANIMAL   HEAT. 

223.  Animal  or  Vital  Heat.  If  a  thermometer,  made  for 
the  purpose,  be  placed  for  five  minutes  in  the  armpit,  or  under 
the  tongue,  it  will  indicate  a  temperature  of  about  98 1°  F., 
whether  the  surrounding  atmosphere  be  warm  or  cold.  This 
is  the  natural  heat  of  a  healthy  person,  and  in  health  it  rarely 
varies  more  than  a  degree  or  two.  But  as  the  body  is  con- 
stantly losing  heat  by  radiation  and  conduction,  it  is  evident 
that  if  the  standard  temperature  be  maintained,  a  certain 
amount  of  heat  must  be  generated  within  the  body  to  make 
up  for  the  loss  externally.  The  heat  thus  produced  is  known 
as  animal  or  vital  heat. 

This  generation  of  heat  is  common  to  all  living  organisms. 
When  the  mass  of  the  body  is  large,  its  heat  is  readily  percep- 
tible to  the  touch  and  by  its  effect  upon  the  thermometer.  In 
mammals  and  birds  the  heat-production  is  more  active  than  in 
fishes  and  reptiles,  and  their  temperatures  differ  in  degree  even 
in  different  species  of  the  same  class,  according  to  the  special 
organization  of  the  animal  and  the  general  activity  of  its  func- 
tions. The  temperature  of  the  frog  may  be  85°  F.  in  June  and 
41°  F.  in  January.  The  structure  of  its  tissues  is  unaltered 
and  their  vitality  unimpaired  by  such  violent  fluctuations.  But 
in  man  it  is  necessary  not  only  for  health,  but  even  for  life,  that 
the  temperature  should  vary  only  within  narrow  limits  around 
the  mean  of  981°  F. 


226  PRACTICAL    PHYSIOLOGY. 

We  are  ignorant  of  the  precise  significance  of  this  constancy 
of  temperature  in  warm-blooded  animals,  which  is  as  important 
and  peculiar  as  their  average  height.  Man,  undoubtedly,  must 
possess  a  superior  delicacy  of  organization,  hardly  revealed  by 
structure,  which  makes  it  necessary  that  he  should  be  shielded 
from  the  shocks  and  jars  of  varying  temperature,  that  less  highly 
endowed  organisms  endure  with  impunity. 

224.  Sources  of  Bodily  Heat.  The  heat  of  the  body  is 
generated  by  the  chemical  changes,  generally  spoken  of  as 
those  of  oxidation,  which  are  constantly  going  on  in  the  tissues. 
Indeed,  whenever  protoplasmic  materials  are  being  oxidized 
(the  process  referred  to  in  sec.  15  as  katabolism)  heat  is  being 
set  free.  These  chemical  changes  are  of  various  kinds,  but 
the  great  source  of  heat  is  the  katabolic  process,  known  as 
oxidation. 

The  vital  part  of  the  tissues,  built  up  from  the  complex 
classes  of  food,  is  oxidized  by  means  of  the  oxygen  carried  by 
the  arterial  blood,  and  broken  down  into  simpler  bodies  which 
at  last  result  in  urea,  carbon  dioxid,  and  water.  Wherever 
there  is  life,  this  process  of  oxidation  is  going  on,  but  more 
energetically  in  some  tissues  and  organs  than  in  others.  In 
other  words,  the  minutest  tissue  in  the  body  is  a  source  of 
heat  in  proportion  to  the  activity  of  its  chemical  changes. 
The  more  active  the  changes,  the  greater  is  the  heat  produced, 
and  the  greater  the  amount  of  urea,  carbon  dioxid,  and  water 
eliminated.  The  waste  caused  by  this  oxidation  must  be 
made  good  by  a  due  supply  of  food  to  be  built  up  into 
protoplasmic  material.  For  the  production  of  heat,  therefore, 
food  is  necessary.  But  the  oxidation  process  is  not  as  simple 
and  direct  as  the  statement  of  it  might  seem  to  indicate. 
Though  complicated  in  its  various  stages,  the  ultimate  result  is 
as  simple  as  in  ordinary  combustion  outside  of  the  body,  and 
the  products  are  the  same. 


RESPIRATION.  22? 

The  continual  chemical  changes,  then,  chiefly  by  oxidation 
of  combustible  materials  in  the  tissues,  produce  an  amount  of 
heat  which  is  efficient  to  maintain  the  temperature  of  the  living 
body  at  about  98^°  F.  This  process  of  oxidation  provides  not 
only  for  the  heat  of  the  body,  but  also  for  the  energy  required 
to  carry  on  the  muscular  work  of  the  animal  organism. 

225.  Regulation  of  the  Bodily  Temperature.  While  bodily 
heat  is  being  continually  produced,  it  is  also  as  continually  being 
lost  by  the  lungs,  by  the  skin,  and  to  some  extent,  by  certain 
excretions.  The  blood,  in  its  swiftly  flowing  current,  carries 
warmth  from  the  tissues  where  heat  is  being  rapidly  generated, 
to  the  tissues  or  organs  in  which  it  is  being  lost  by  radiation, 
conduction,  or  evaporation.  Were  there  no  arrangement  by 
which  heat  could  be  distributed  and  regulated,  the  temperature 
of  the  body  would  be  very  unequal  in  different  parts,  and 
would  vary  at  different  times. 

The  normal  temperature  is  maintained  with  slight  variations 
throughout  life.  Indeed  a  change  of  more  than  a  degree  above 
or  below  the  average,  indicates  some  failure  in  the  organism,  or 
some  unusual  influence.  It  is  evident,  then,  that  the  mechan- 
isms which  regulate  the  temperature  of  the  body  must  be 
exceedingly  sensitive. 

The  two  chief  means  of  regulating  the  temperature  of  the 
body  are  the  lungs  and  the  skin.  As  a  means  of  lowering 
the  temperature,  the  lungs  and  air  passages  are  very  inferior  to 
the  skin ;  although,  by  giving  heat  to  the  air  we  breathe,  they 
stand  next  to  the  skin  in  importance.  As  a  regulating  power 
they  are  altogether  subordinate  to  the  skin. 

Experiment  113.  To  show  the  natural  temperature  of  the  body.  Bor- 
row a  physician's  clinical  thermometer,  and  take  your  own  temperature, 
and  that  of  several  friends,  by  placing  the  instrument  under  the  tongue, 
closing  the  mouth,  and  holding  it  there  for  five  minutes.  It  should  be 
thoroughly  cleansed  after  each  use. 


228  PRACTICAL    PHYSIOLOGY. 

226.  The  Skin  as  a  Heat-regulator.  The  great 'regulator 
of  the  bodily  temperature  is,  undoubtedly,  the  skin,  which  per- 
forms this  function  by  means  of  a  self-regulating  apparatus  with 
a  more  or  less  double  action.  First,  the  skin  regulates  the  loss 
of  heat  by  means  of  the  vaso-motor  mechanism.  The  more 
blood  passes  through  the  skin,  the  greater  will  be  the  loss  of 
heat  by  conduction,  radiation,  and  evaporation.  Hence,  any 
action  of  the  vaso-motor  mechanism  which  causes  dilatation 
of  the  cutaneous  capillaries,  leads  to  a  larger  flow  of  blood 
through  the  skin,  and  will  tend  to  cool  the  body.  On  the 
other  hand,  when  by  the  same  mechanism  the  cutaneous 
vessels  are  constricted,  there  will  be  a  smaller  flow  of  blood 
through  the  skin,  which  will  serve  to  check  the  loss  of  heat 
from  the  body  (sees.  195  and  270). 

Again,  the  special  nerves  of  perspiration  act  directly  as 
regulators  of  temperature.  They  increase  the  loss  of  heat 
when  they  promote  the  secretion  of  the  skin,  and  diminish  the 
loss  when  they  cease  to  promote  it. 

The  practical  working  of  this  heat-regulating  mechanism  is 
well  shown  by  exercise.  The  bodily  temperature  rarely  rises 
so  much  as  a  degree  during  vigorous  exercise.  The  respiration 
is  increased,  the  cutaneous  capillaries  become  dilated  from  the 
quickened  circulation,  and  a  larger  amount  of  blood  is  circulat- 
ing through  the  skin.  Besides  this,  the  skin  perspires  freely. 
A  large  amount  of  heat  is  thus  lost  to  the  body,  sufficient  to 
offset  the  addition  caused  by  the  muscular  contractions. 

It  is  owing  to  the  wonderful  elasticity  of  the  sweat-secreting 
mechanism,  and  to  the  increase  in  respiratory  activity,  and  the 
consequent  increase  in  the  amount  of  watery  vapor  given  off 
by  the  lungs,  that  men  are  able  to  endure  for  days  an  atmo- 
sphere warmer  than  the  blood,  and  even  for  a  short  time  at  a 
temperature  above  that  of  boiling  water.  The  temperature  of 
a  Turkish  bath  may  be  as  high  as  150°  to  175°  F.  But  an  atmo- 
spheric temperature  may  be  considerably  below  this,  and  yet 


RESPIRATION.  32Q 

if  long  continued  becomes  dangerous  to  life.  In  August,  1896, 
for  instance,  hundreds  of  persons  died  in  this  country,  within 
a  few  days,  from  the  effects  of  the  excessive  heat. 

A  much  higher  temperature  may  be  borne  in  dry  air  than  in 
humid  air,  or  that  which  is  saturated  with  watery  vapor.  Thus, 
a  shade  temperature  of  100°  F.  in  the  dry  air  of  a  high  plain 
may  be  quite  tolerable,  while  a  temperature  of  80°  F.  in  the 
moisture-laden  atmosphere  of  less  elevated  regions,  is  oppres- 
sive. The  reason  is  that  in  dry  air  the  sweat  evaporates  freely, 
and  cools  the  skin.  In  saturated  air  at  the  bodily  temperature 
there  is  little  loss  of  heat  by  perspiration,  or  by  evaporation 
from  the  bodily  surface. 

This  topic  is  again  discussed  in  the  description  of  the  skin 
as  a  regulator  of  the  bodily  temperature  (sec.  241). 

227.   Voluntary  Means  of  Regulating  the  Temperature. 

The  voluntary  factor,  as  a  means  of  regulating  the  heat  loss 
in  man,  is  one  of  great  importance.  Clothing  retards  the  loss 
of  heat  by  keeping  in  contact  with  it  a  layer  of  still  air,  which 
is  an  exceedingly  bad  conductor.  When  a  man  feels  too  warm 
and  throws  off  his  coat,  he  removes  one  of  the  badly  conduct- 
ing layers  of  air,  and  increases  the  heat  loss  by  radiation  and 
conduction.  The  vapor  next  the  skin  is  thus  allowed  a  freer 
access  to  the  surface,  and  the  loss  of  heat  by  evaporation  of 
the  sweat  becomes  greater.  This  voluntary  factor  by  which 
the  equilibrium  is  maintained  must  be  regarded  as  of  great 
importance.  This  power  also  exists  in  the  lower  animals,  but 
to  a  much  smaller  extent.  Thus  a  dog,  on  a  hot  day,  runs  out 
his  tongue  and  stretches  his  limbs  so  as  to  increase  the  sur- 
face from  which  heat  is  radiated  and  conducted. 

The  production,  like  the  loss,  of  heat  is  to  a  certain  extent 
under  the  control  of  the  will.  Work  increases  the  production 
of  heat,  and  rest,  especially  sleep,  less.ens  it.  Thus  the  inhab- 
itants of  very  hot  countries  seek  relief  during  the  hottest  part 


23O  PRACTICAL    PHYSIOLOGY. 

of  the  day  by  a  siesta.  The  quantity  and  quality  of  food  also 
influence  the  production  of  heat.  A  larger  quantity  of  food  is 
taken  in  winter  than  in  summer.  Among  the  inhabitants  of 
the  northern  and  Arctic  regions,  the  daily  consumption  of  food 
is  far  greater  than  in  temperate  and  tropical  climates. 

228.  Effect  of  Alcohol  upon  the  Lungs.  It  is  a  well  recog- 
nized fact  that  alcohol  when  taken  into  the  stomach  is  carried 
from  that  organ  to  the  liver,  where,  by  the  baneful  directness 
of  its  presence,  it  produces  a  speedy  and  often  disastrous  effect. 
But  the  trail  of  its  malign  power  does  not  disappear  there. 
From  the  liver  it  passes  to  the  right  side  of  the  heart,  and 
thence  to  the  lungs,  where  its  influence  is  still  for  harm. 

In  the  lungs,  alcohol  tends  to  check  and  diminish  the  breath- 
ing capacity  of  these  organs.  This  effect  follows  from  the 
partial  paralyzing  influence  of  the  stupefying  agent  upon  the 
sympathetic  nervous  system,  diminishing  its  sensibility  to  the 
impulse  of  healthful  respiration.  This  diminished  capacity 
for  respiration  is  clearly  shown  by  the  use  of  the  spirometer,  a 
simple  instrument  which  accurately  records  the  cubic  measure 
of  the  lungs,  and  proves  beyond  denial  the  decrease  of  the 
lung  space. 

"  Most  familiar  and  most  dangerous  is  the  drinking  man's  inability  to  resist  lung 
diseases." —  DR.  ADOLPH  FRICK,  the  eminent  German  physiologist  of  Zurich. 

"  Alcohol,  instead  of  preventing  consumption,  as  was  once  believed,  reduces  the 
vitality  so  much  as  to  render  the  system  unusually  susceptible  to  that  fatal  disease." 
—  R.  S.  TRACY,  M.D.,  Sanitary  Inspector  of  the  N.  Y.  City  Health  Dept. 

"  In  thirty  cases  in  which  alcoholic  phthisis  was  present  a  dense,  fibroid,  pigmented 
change  was  almost  invariably  present  in  some  portion  of  the  lung  far  more  frequently 
than  in  other  cases  of  phthisis."  —  Annual  of  Medical  Sciences. 

"  There  is  no  form  of  consumption  so  fatal  as  that  from  alcohol.  Medicines  affect 
the  disease  but  little,  the  most  judicious  diet  fails,  and  change  of  air  accomplishes 
but  slight  real  good.  ...  In  plain  terms,  there  is  no  remedy  whatever  for  alcoholic 
phthisis.  It  may  be  delayed  in  its  course,  but  it  is  never  stopped ;  and  not  infre- 
quently, instead  of  being  delayed,  it  runs  on  to  a  fatal  termination  more  rapidly  than 
is  common  in  any  other  type  of  the  disorder."  —  DR.  B.  W.  RICHARDSON  in  Diseases 
of  Modern  Life. 


RESPIRATION.  231 

229.  Other  Results  of  Intoxicants  upon  the  Lungs.  But 
a  more  potent  injury  to  the  lungs  comes  from  another  cause. 
The  lungs  are  the  arena  where  is  carried  on  the  ceaseless  inter- 
change of  elements  that  is  necessary  to  the  processes  of  life. 
Here  the  dark  venous  blood,  loaded  with  effete  material,  lays 
down  its  carbon  burden  and,  with  the  brightening  company  of 
oxygen,  begins  again  its  circuit.  But  the  enemy  intrudes,  and 
the  use  of  alcohol  tends  to  prevent  this  benign  interchange. 

The  continued  congestion  of  the  lung  tissue  results  in  its  be- 
coming thickened  and  hardened,  thus  obstructing  the  absorption 
of  oxygen,  and  the  escape  of  carbon  dioxid.  Besides  this,  alcohol 
destroys  the  integrity  of  the  red  globules,  causing  them  to 
shrink  and  harden,  and  impairing  their  power  to  receive  oxygen. 
Thus  the  blood  that  leaves  the  lungs  conveys  an  excess  of  the 
poisonous  carbon  dioxid,  and  a  deficiency  of  the  needful  oxy- 
gen. This  is  plainly  shown  in  the  purplish  countenance  of  the 
inebriate,  crowded  with  enlarged  veins.  This  discoloration  of 
the  face  is  in  a  measure  reproduced  upon  the  congested  mu- 
cous membrane  of  the  lungs.  It  is  also  proved  beyond  ques- 
tion by  the  decreased  amount  of  carbon  dioxid  thrown  off  in 
the  expired  breath  of  any  person  who  has  used  alcoholics. 

The  enfeebled  respiration  explains  (though  it  is  only  one  of 
the  reasons)  why  inebriates  cannot  endure  vigorous  and  pro- 
longed exertion  as  can  a  healthy  person.  The  hurried  circu- 
lation produced  by  intoxicants  involves  in  turn  quickened 
respiration,  which  means  more  rapid  exhaustion  of  the  life 
forces.  The  use  of  intoxicants  involves  a  repeated  dilatation 
of  the  capillaries,  which  steadily  diminishes  their  defensive 
power,  rendering  the  person  more  liable  to  yield  to  the  in- 
vasion of  pulmonary  diseases.1 

1 "  The  lungs  from  the  congested  state  of  their  vessels  produced  by  alcohol  are  more 
subject  to  the  influence  of  cold,  the  result  being  frequent  attacks  of  bronchitis.  It  has 
been  recognized  of  late  years  that  there  is  a  peculiar  form  of  consumption  of  the 
lungs  which  is  very  rapidly  fatal  and  found  only  in  alcohol  drinkers."  —  PROFESSOR 
H.  NEWELL  MARTIN. 


232  PRACTICAL  PHYSIOLOGY. 

230.  Effect  of  Alcoholics  upon  Disease.     A  theory  has  pre- 
vailed, to  a  limited  extent,  that  the  use  of  intoxicants  may  act 
as   a   preventive    of    consumption.       The    records   of    medical 
science  fail  to  show  any  proof  whatever  to  support  this  impres- 
sion.     No  error  could  be  more  serious  or  more  misleading, 
for  the  truth   is   in  precisely  the  opposite  direction.     Instead 
of  preventing,  alcohol  tends  to  develop  consumption.     Many 
physicians  of  large  experience  record  the  existence  of  a  dis- 
tinctly   recognized    alcoholic    consumption,    attacking     those 
constitutions    broken     down    by    dissipation.      This   form   of 
consumption  is  steadily  progressive,  and  always  fatal. 

The  constitutional  debility  produced  by  the  habit  of  using 
alcoholic  beverages  tends  to  render  one  a  prompt  victim  to  the 
more  severe  diseases,  as  pneumonia,  and  especially  epidemical 
diseases,  which  sweep  away  vast  numbers  of  victims  every  year. 

231.  Effect  of  Tobacco  upon  the  Respiratory  Passages. 
The  effects  of  tobacco  upon  the  throat    and   lungs  are  fre- 
quently very  marked  and  persistent.     The  hot  smoke   must 
very  naturally  be  an  irritant,  as  the  mouth  and  nostrils  were 
not  made  as  a  chimney  for  heated  and  narcotic  vapors.     The 
smoke  is  an  irritant,  both  by  its  temperature  and  from  its  de- 
structive ingredients,  the  carbon  soot  and  the  ammonia  which 
it  conveys.     It  irritates   and  dries   the  mucous   membrane   of 
the  mouth  and  throat,  producing  an  unnatural  thirst  which  be- 
comes an  enticement  to  the  use  of  intoxicating  liquors.     The 
inflammation  of  the  mouth  and  throat  is  apt  to  extend  up  the 
Eustachian  tube,  thus  impairing  the  sense  of  hearing. 

But  even  these  are  not  all  the  bad  effects  of  tobacco.  The 
inhalation  of  the  poisonous  smoke  produces  unhealthful  effects 
upon  the  delicate  mucous  membrane  of  the  bronchial  tubes 
and  of  the  lungs.  Upon  the  former  the  effect  is  to  produce 
an  irritating  cough,  with  short  breath  and  chronic  bronchial 
catarrh.  The  pulmonary  membrane  is  congested,  taking  cold 


RESPIRATION.  233 

becomes  easy,  and  recovery  from  it  tedious.  Frequently  the 
respiration  is  seriously  disturbed,  thus  the  blood  is  imperfectly 
aerated,  and  so  in  turn  the  nutrition  of  the ,  entire  system  is 
impaired.  The  cigarette  is  the  defiling  medium  through  which 
these  direful  results  frequently  invade  the  system,  and  the 
easily  moulded  condition  of  youth  yields  readily  to  the  destruc- 
tive snare. 

"  TJie  first  effect  of  a  cigar  upon  any  one  demonstrates  that  tobacco  can  poison  by 
its  smoke  and  through  the  lungs."  —  London  Lancet, 

"  The  action  of  the  heart  and  lungs  is  impaired  by  the  influence  of  the  narcotic  on 
the  nervous  system,  but  a  morbid  state  of  the  larynx,  trachea,  and  lungs  results  from 
the  direct  action  of  the  smoke."  — r  DR.  LAYCOCK,  Professor  of  Medicine  in  the 
University  of  Edinburgh. 

ADDITIONAL    EXPERIMENTS. 

Experiment  114.  To  illustrate  the  arrangement  of  the  lungs  and  the 
two  pleura.  Place  a  large  sponge  which  will  represent  the  lungs  in  a  thin 
paper  bag  which  just  fits  it ;  this  will  represent  the  pulmonary  layer  of  the 
pleura.  Place  the  sponge  and  paper  bag  inside  a  second  paper  bag,  which 
will  represent  the  parietal  layer  of  the  pleura.  Join  the  mouths  of  the  two 
bags.  The  two  surfaces  of  the  bags  which  are  now  in  contact  will  represent 
the  two  moistened  surfaces  of  the  pleurae,  which  rub  together  in  breathing. 

Experiment  115.  To  show  how  the  lungs  may  be  filled  with  air.  Take 
one  of  the  lungs  saved  from  Experiment  1 10.  Tie  a  glass  tube  six  inches 
long  into  the  larynx.  Attach  a  piece  of  rubber  to  one  end  of  the  glass  tube. 
Now  inflate  the  lung  several  times,  and  let  it  collapse.  When  distended, 
examine  every  part  of  it. 

Experiment  116.  To  take  your  own  bodily  temperature  or  that  of  a 
friend.  If  you  cannot  obtain  the  use  of  a  physician's  clinical  thermometer, 
unfasten  one  of  the  little  thermometers  found  on  so  many  calendars  and 
advertising  sheets.  Hold  it  for  five  minutes  under  the  tongue  with  the  lips 
closed.  Read  it  while  in  position  or  the  instant  it  is  removed.  The  natural 
temperature  of  the  mouth  is  about  98^°  F. 

Experiment  117.  To  show  the  vocal  cords.  Get  a  pig's  windpipe  in 
perfect  order,  from  the  butcher,  to  show  the  vocal  cords.  Once  secured,  it 
can  be  kept  for  an  indefinite  time  in  glycerine  and  water  or  dilute  alcohol. 

Experiment  118.  To  show  that  the  air  we  expire  is  warm.  Breathe  on 
a  thermometer  for  a  few  minutes.  The  mercury  will  rise  rapidly. 


234 


PRACTICAL    PHYSIOLOGY. 


Experiment  119.  To  show  that  expired  air  is  moist.  Breathe  on  a 
mirror,  or  a  knife  blade,  or  any  polished  metallic  surface,  and  note  the 
deposit  of  moisture. 

Experiment  1 20.    To  show  that  the  expired  air  contains  carbon  dioxtd.    Put 
a  glass  tube  into  a  bottle  of  lime  water  and  breathe  through  the  tube.    The 
A  liquid  will  soon  become  cloudy,  because  the  carbon  dioxid 

of  the  expired  air  throws  down  the  lime  held  in  solution. 

Experiment  121.  "A  substitute  for  a  clinical  ther- 
mometer may  be  readily  contrived  by  taking  an  ordinary 
house  thermometer  from  its  tin  case,  and  cutting  off  the 
lower  part  of  the  scale  so  that  the  bulb  may  project  freely. 
With  this  instrument  the  pupils  may  take  their  own  and 
each  other's  temperatures,  and  it  will  be  found  that  what- 
ever the  season  of  the  year  or  the  temperature  of  the 
room,  the  thermometer  in  the  mouth  will  record  about 
99°  F.  Care  must,  of  course,  be  taken  to  keep  the  ther- 
mometer in  the  mouth  till  it  ceases  to  rise,  and  to  read 
while  it  is  still  in  position." —  PROFESSOR  H.  P.  BOWDITCH. 

Experiment  122.  To  illustrate  the  manner  in  which  the 
movements  of  inspiration  cause  the  air  to  enter  the  lungs. 
Fit  up  an  apparatus,  as  represented  in  Fig.  95,  in  which  a 
stout  glass  tube  is  provided  with  a  sound  cork,  B,  and  also 
an  air-tight  piston,  D,  resembling  that  of  an  ordinary 
syringe.  A  short  tube,  A,  passing  through  the  cork,  has  a 
small  India-rubber  bag,  C,  tied  to  it.  Fit  the  cork  in  the 
tube  while  the  piston  is  near  the  top.  Now,  by  lowering 
the  piston  we  increase  the  capacity  of  the  cavity  containing 
the  bag.  The  pressure  outside  the  bag  is  thus  lowered, 
and  air  rushes  into  it  through  the  tube,  A,  till  a  balance  is 
restored.  The  bag  is  thus  stretched.  As  soon  as  we  let 
§°  the  Piston»  tne  elasticity  of  the  bag,  being  free  to  act, 

Movements    of    drives  out  the  air  just  taken  in,  and  the  piston  returns  to 

Respiration.         its  former  place. 


FIG.  95. 

Apparatus       for 
Illustrating  the 


It  will  be  noticed  that  in  this  experiment  the  elastic  bag  and  its  tube 
represent  the  lungs  and  trachea;  and  the  glass  vessel  enclosing  it,  the 
thorax. 

For  additional  experiments  on  the  mechanics  of  respiration,  see  Chap- 
ter XV. 


CHAPTER   IX. 
THE    SKIN    AND    THE    KIDNEYS. 

232.  The  Elimination  of  Waste  Products.  We  have  traced 
the  food  from  the  alimentary  canal  into  the  blood.  We  have 
learned  that  various  food  materials,  prepared  by  the  diges- 
tive processes,  are  taken  up  by  the  branches  of  the  portal  vein, 
or  by  the  lymphatics,  and  carried  into  the  blood  current.  The 
nutritive  material  thus  absorbed  is  conveyed  by  the  blood 
plasma  and  the  lymph  to  the  various  tissues  to  provide  them 
with  nourishment. 

We  have  learned  also  that  oxygen,  taken  up  in  the  air  cells 
of  the  lungs,  is  being  continually  carried  to  the  tissues,  and  that 
the  blood  is  purified  by  being  deprived  in  the  lungs  of  its  excess 
of  carbon  dioxid.  From  this  tissue  activity,  which  is  mainly 
oxidation,  are  formed  certain  waste  products  which,  as  we  have 
seen,  are  absorbed  by  the  capillaries  and  lymphatics  and  carried 
into  the  venous  circulation. 

In  their  passage  through  the  blood  and  tissues,  the  albu- 
mens, sugars,  starches,  and  fats  are  converted  into  carbon 
dioxid,  water,  and  urea,  or  some  closely  allied  body.  Certain 
articles  of  food  also  contain  small  amounts  of  sulphur  and  phos- 
phorus, which  undergo  oxidation  into  sulphates  and  phosphates. 
We  speak,  then,  of  carbon  dioxid,  salts,  and  water  as  waste 
products  of  the  animal  economy.  These  leave  the  body  by 
one  of  the  three  main  channels,  —  the  lungs,  the  skin,  or  the 
kidneys. 

The  elimination  of  these  products  is  brought  about  by  a 
special  apparatus  called  organs  of  excretion.  The  worn-out 
substances  themselves  are  called  excretions,  as  opposed  to 


236 


PRACTICAL    PHYSIOLOGY. 


secretions,  which  are  elaborated  for  use  in  the  body.  (See 
note,  p.  121.)  As  already  shown,  the  lungs  are  the  main 
channels  for  the  elimination  of  carbon  dioxid,  and  of  a  portion 
of  water  as  vapor.  By  the  skin  the  body  gets  rid  of  a  small 
portion  of  salts,  a  little  carbon  dioxid,  and  a  large  amount  of 
water  in  the  form  of  perspiration.  From  the  kidneys  are 
eliminated  nearly  all  the  urea  and  allied  bodies,  the  main 

portion  of  the  salts,  and  a  large 
amount  of  water.  In  fact,  practi- 
cally all  the  nitrogenous  waste 
leaves  the  body  by  the  kidneys. 


of  the  renal  epithelium  ;    S,  the  skin  ; 
o,  oxygen  ;   h,  hydrogen;   n,  nitrogen. 


233.    The  Skin.     The  skin  is 

an  important  and  unique  organ  of 
the  body.     It  is  a  blood-purifying 
organ  as  truly  as  are  the  lungs  and 
the  kidneys,  while  it  also  performs 
FIG.  96. -Diagrammatic  Scheme  to    other  and  complex  duties.     It  is 
illustrate  in  a  very  General  Way    not  merely  a  protective  covering 

Absorption  and  Excretion.  for  ^  surface  of  the  body       This 

A,  represents  the  alimentary  canal ;!-,..,,,  . 

the  pulmonary  surface;K,  the  surface     1S    mdeed    the    HlOSt    apparent,  but 

in  some  respects  the  least  im- 
portant, of  its  functions.  This 
protective  duty  is  necessary  and  efficient,  as  is  proved  by  the 
familar  experience  of  the  pain  when  a  portion  of  the  outer  skin 
has  been  removed. 

The  skin,  being  richly  supplied  with  nerves,  is  an  important 
organ  of  sensibility  and  touch.  In  some  parts  it  is  closely 
attached  to  the  structures  beneath,  while  in  others  it  is  less 
firmly  adherent  and  rests  upon  a  variable  amount  of  fatty 
tissue.  It  thus  assists  in  relieving  the  abrupt  projections  and 
depressions  of  the  general  surface,  and  in  giving  roundness 
and  symmetry  to  the  entire  body.  The  thickness  of  the  skin 
varies  in  different  parts  of  the  body.  Where  exposed  to  pres- 


THE  SKIN  AND  THE  KIDNEYS.  237 

sure  and  friction,  as  on  the  soles  of  the  feet  and  in  the  palms 
of  the  hands,  it  is  much  thickened. 

The  true  skin  is  T^  to  £  of  an  inch  in  thickness,  but  in  certain 
parts,  as  in  the  lips  and  ear  passages,  it  is  often  not  more  than 
Ti^  of  an  inch  thick.  At  the  orifices  of  the  body,  as  at  the 
mouth,  ears,  and  nose,  the  skin  gradually  passes  into  mucous 
membrane,  the  structure  of 
the  two  being  practically 
identical.  As  the  skin  is  an 
outside  covering,  so  is  the 
mucous  membrane  a  more 
delicate  inside  lining  for  all 

Cavities    into  Which  the  aper-     FIG.  97- -  A  Layer  of  the  Cuticle  from  the 
tures  Open,  as  the  alimentary        Palm  of  the  Hand.     (Detached  by  macer- 

canal  and  the  lungs.  ation.) 

The  skin  ranks  as  an  important  organ  of  excretion,  its  product 
being  sweat,  excreted  by  the  sweat  glands.  The  amount  of  this 
excretion  evaporated  from  the  general  surface  is  very  consider- 
able, and  is  modified  as  becomes  necessary  from  the  varied  con- 
ditions of  the  temperature.  The  skin  also  plays  an  important 
part  in  regulating  the  bodily  temperature  (sec.  241). 

234.  The  Cutis  Vera,  or  True  Skin.  The  skin  is  remark- 
ably complex  in  its  structure,  and  is  divided  into  two  distinct 
layers,  which  may  be  readily  separated:  the  deeper  layer, — 
the  true  skin,  dermis,  or  corium ;  and  the  superficial  layer,  or 
outer  skin,  —  the  epidermis,  cuticle,  or  scarf  skin. 

The  true  skin  consists  of  elastic  and  white  fibrous  tissue, 
the  bundles  of  which  interlace  in  every  direction.  Throughout 
this  feltwork  structure  which  gradually  passes  into  areolar  tis- 
sue are  numerous  muscular  fibers,  as  about  the  hair-follicles 
and  the  oil  glands.  When  these  tiny  muscles  contract  from 
cold  or  by  mental  emotion,  the  follicles  project  upon  the  surface, 
producing  what  is  called  "goose  flesh." 


238  PRACTICAL    PHYSIOLOGY. 

The  true  skin  is  richly  supplied  with  blood-vessels  and 
nerves,  as  when  cut  it  bleeds  freely,  and  is  very  sensitive.  The 
surface  of  the  true  skin  is  thrown  into  a  series  of  minute  eleva- 
tions called  the  papillae,  upon  which  the  outer  skin  is  moulded. 
These  abound  in  blood-vessels,  lymphatics,  and  peculiar  nerve- 
endings,  which  will  be  described  in  connection  with  the  organ 
of  touch  (sec.  314).  The  papillae  are  large  and  numerous  in 
sensitive  places,  as  the  palms  of  the  hands,  the  soles  of  the 
feet,  and  the  fingers.  They  are  arranged  in  parallel  curved 
lines,  and  form  the  elevated  ridges  seen  on  the  surface  of  the 
outer  skin  (Fig.  103). 

235.  The  Epidermis,  or  Cuticle.  Above  the  true  skin  is  the 
epidermis.  It  is  semi-transparent,  and  under  the  microscope 
resembles  the  scales  of  a  fish.  It  is  this  layer  that  is  raised 
by  a  blister. 

As  the  epidermis  has  neither  blood-vessels,  nerves,  nor  lym- 
phatics, it  may  be  cut  without  bleeding  or  pain.  Its  outer 
surface  is  marked  with  shallow  grooves  which  correspond  to 
the  deep  furrows  between  the  papillae  of  the  true  skin.  The 
inner  surface  is  applied  directly  to  the  papillary  layer  of  the 
true  skin,  and  follows  closely  its  inequalities.  The  outer  skin 
is  made  up  of  several  layers  of  cells,  which  next  to  the  true 
skin  are  soft  and  active,  but  gradually  become  harder  towards 
the  surface,  where  they  are  flattened  and  scale-like.  The 
upper  scales  are  continually  being  rubbed  off,  and  are  replaced 
by  deeper  cells  from  beneath.  There  are  new  cells  continually 
being  produced  in  the  deeper  layer,  which  push  upward  the 
cells  already  existing,  then  gradually  become  dry,  and  are  cast 
off  as  fine,  white  dust.  Rubbing  with  a  coarse  towel  after  a 
hot  bath  removes  countless  numbers  of  these  dead  cells  of  the 
outer  skin.  During  and  after  an  attack  of  scarlet  fever  the 
patient  "  peels,"  that  is,  sheds  an  unusual  amount  of  the  scaly 
cells  of  the  cuticle. 


THE    SKIN    AND    THE    KIDNEYS. 


239 


The  deeper  and  more  active  layer  of  the  epidermis,  the 
mucosum,  is  made  up  of  cells  some  of  which  contain  minute 
granules  of  pigment,  or  coloring  matter,  that  give  color  to  the 
skin.  The  differences  in  the  tint,  as  brunette,  fair,  and  blond, 
are  due  mainly  to  the  amount  of  coloring  matter  in  these  pig- 
ment cells.  In  the  European  this  amount  is  generally  small, 
while  in  other  peoples  the  color  cells  may  be  brown,  yellow,  or 


FIG.  98.  —  Surface  of  the  Palm  of  the  Hand,  showing  the  Openings  of  the  Sweat 
Glands  and  the  Grooves  between  the  Papillae  of  the  Skin.  (Magnified  4 
diameters.)  [In  the  smaller  figure  the  same  epidermal  surface  is  shown,  as 
seen  with  the  naked  eye.] 

even  black.  The  pinkish  tint  of  healthy  skin,  and  the  rosy-red 
after  a  bath  are  due,  not  to  the  pigment  cells,  but  to  the  pres- 
sure of  capillaries  in  the  true  skin,  the  color  of  the  blood  being 
seen  through  the  semi-transparent  outer  skin. 

Experiment  123.  Of  course  the  living  skin  can  be  examined  only  in  a 
general  way.  Stretch  and  pull  it,  and  notice  that  it  is  elastic.  Note  any 
liver  spots,  white  scars,  moles,  warts,  etc.  Examine  the  outer  skin  care- 
fully with  a  strong  magnifying  glass.  Study  the  papillae  on  the  palms. 
Scrape  off  with  a  sharp  knife  a  few  bits  of  the  scarf  skin,  and  examine 
them  with  the  microscope. 

236.  The  Hair.  Hairs  varying  in  size  cover  nearly  the 
entire  body,  except  a  few  portions,  as  the  upper  eyelids,  the 
palms  of  the  hands,  and  the  soles  of  the  feet. 

The  length  and  diameter  of  the  hairs  vary  in  different  per- 
sons, especially  in  the  long,  soft  hairs  of  the  head  and  beard. 
The  average  number  of  hairs  upon  a  square  inch  of  the  scalp  is 
about  1000,  and  the  number  upon  the  entire  head  is  estimated 
as  about  120,000. 


240 


PRACTICAL    PHYSIOLOGY. 


Healthy  hair  is  quite  elastic,  and  may  be  stretched  from 
one-fifth  to  one-third  more  than  its  original  length.  An  ordi- 
nary hair  from  the  head  will  support  a  weight  of  six  to  seven 
ounces.  The  hair  may  become  strongly  electrified  by  friction, 
especially  when  brushed  vigorously  in  cold,  dry  weather.  An- 
other peculiarity  of  the  hair  is  that  it  readily  absorbs  moisture. 

237.  Structure  of  the  Hair.  The  hair  and  the  nails  are 
structures  connected  with  the  skin,  being  modified  forms  of 
the  epidermis.  A  hair  is  formed  by  a  depression,  or  furrow, 
the  inner  walls  of  which  consist  of  the  infolded  outer  skin. 
This  depression  takes  the  form  of  a  sac  and 
is  called  the  hair-follicle,  in  which  the  roots 
of  the  hair  are  embedded.  At  the  bottom 
of  the  follicle  there  is  an  upward  projec- 
tion of  the  true  skin,  a  papilla,  which  con- 
tains blood-vessels  and  nerves.  It  is  covered 
with  epidermic  cells  which  multiply  rapidly, 
thus  accounting  for  the  rapid  growth  of  the 
hair.  Around  each  papilla  is  a  bulbous 
expansion,  the  hair  bulb,  from  which  the 
hair  begins  to  grow. 

The  cells  on  the  papilla  are  the  means  by 
which  the  hairs  grow.  As  these  are  pushed 
upwards  by  new  ones  formed  beneath,  they 
are  compressed,  and  the  shape  of  the  follicle 
determines  their  cylindrical  growth,  the  shaft 
of  the  hair.  So  closely  are  these  cells  welded  to  form  the 
cylinder,  that  even  under  a  microscope  the  hair  presents  only  a 
fibrous  appearance,  except  in  the  center,  where  the  cells  are 
larger,  forming  the  medulla,  or  pith  (Fig.  106). 

The  medulla  of  the  hair  contains  the  pigment  granules  or 
coloring  matter,  which  may  be  of  any  shade  between  a  light 
yellow  and  an  intense  black.  It  is  this  that  gives  the  great 


FIG.  99.  —  Epidermis 
of  the  Foot. 

It  will  be  noticed  that 
there  are  only  a  few 
orifices  of  the  sweat 
glands  in  this  region. 
(Magnified  8  diam- 
eters.) 


THE    SKIN    AND    THE    KIDNEYS. 


24I 


variety  in  color.  Generally  with  old  people  the  pigment  is 
absent,  the  cells  being  occupied  by  air;  hence  the  hair  becomes 
gray  or  white.  The  thin,  flat  scales  on  the  surface  of  the  hair 
overlap  like  shingles.  Connected  with  the  hair-follicles  are 
small  bundles  of  muscular  fibers,  which  run 
obliquely  in  the  skin  and  which,  on  shorten- 
ing, may  cause  the  hairs  to  become  more 
upright,  and  thus  are  made  to  "  stand  on 
end."  The  bristling  back  of  an  angry  cat 
furnishes  a  familiar  illustration  of  this  mus- 
cular action. 

Opening  into  each  hair-follicle  are  usually 
one  or  more  sebaceous,  or  oil,  glands. 
These  consist  of  groups  of  minute  pouches 
lined  with  cells  producing  an  oily  material 
which  serves  to  oil  the  hair  and  keep  the 
skin  moist  and  pliant. 


238.  The  Nails.  The  nails  are  also 
formed  of  epidermis  cells  which  have 
undergone  compression,  much  like  those 
forming  the  shaft  of  a  hair.  In  other 
words,  a  nail  is  simply  a  thick  layer  of 
horny  scales  built  from  the  outer  part  of 
the  scarf  skin.  The  nail  lies  upon  very 
fine  and  closely  set  papillae,  forming  its 
matrix,  or  bed.  It  is  covered  at  its  base 
with  a  fold  of  the  true  skin,  called  its  root, 
from  beneath  which  it  seems  to  grow. 

The  growth  of  the  nail,  like  that  of  the  hair  and  the  outer 
skin,  is  effected  by  the  production  of  new  cells  at  the  root  and 
under  surface.  The  growth  of  each  hair  is  limited  ;  in  time  it 
falls  out  and  is  replaced  by  a  new  one.  But  the  nail  is  kept 
of  proper  size  simply  by  the  removal  of  its  free  edge. 


FIG.  loo.—  Hair  and 

Hair-Follicle. 
A,  root  of  hair;  B,  bulb  of 
the  hair ;  C,  internal  root 
sheath;  D,  external  root 
sheath ;  E,  external  mem- 
brane of  follicle  ;  F,  mus- 
cular fibers  attached  to 
the  follicle  ;  H,  compound 
sebaceous  gland  with  its 
duct,  K ;  L,  simple  seba- 
ceous gland;  M,  opening 
of  the  hair-follicle. 


242 


PRACTICAL    PHYSIOLOGY. 


239.  The  Sweat  Glands.  Deep  in  the  substance  of  the 
true  skin,  or  in  the  fatty  tissue  beneath  it,  are  the  sweat  glands. 
Each  gland  consists  of  a  single  tube  with  a  blind  end,  coiled  in 
a  sort  of  ball  about  ^  of  an  inch  in  diameter.  From  this  coil 
the  tube  passes  upwards  through  the  dermis  in  a  wavy  course 
until  it  reaches  the  cuticle,  which  it  penetrates  with  a  number 
of  spiral  turns,  at  last  opening  on  the  surface.  The  tubes  con- 
sist of  delicate  walls  of  membrane  lined  with  cells.  The  coil  of 


FIG.  101.  —  Concave  or  Adher- 
ent Surface  of  the  Nail. 

A,  border  of  the  root ;  B,  whitish 
portion  of  semi-lunar  shape 
(the  lunula);  C,  body  of  nail. 
The  continuous  line  around 
border  represents  the  free 
edge. 


FIG.  1 02. —  Nail  in  Position. 
A,  section  of  cutaneous  fold  (B)  turned  back 
to  show  the  root  of  the  nail ;  B,  cutaneous 
fold  covering  the  root  of  the  nail;  C, 
semi-lunar  whitish  portion  (lunula);  D, 
free  border. 


the  gland  is  enveloped  by  minute  blood-vessels.  The  cells  of 
the  glands  are  separated  from  the  blood  only  by  a  fine  partition, 
and  draw  from  it  whatever  supplies  they  need  for  their  special 
work. 

With  few  exceptions  every  portion  of  the  skin  is  provided 
with  sweat  glands,  but  they  are  not  equally  distributed  over 
the  body.  They  are  fewest  in  the  back  and  neck,  where  it  is 
estimated  they  average  400  to  the  square  inch.  They  are 
thickest  in  the  palms  of  the  hands,  where  they  amount  to 
nearly  3000  to  each  square  inch.  These  minute  openings 
occur  in  the  ridges  of  the  skin,  and  may  be  easily  seen  with  a 
hand  lens.  The  length  of  a  tube  when  straightened  is  about 


THE    SKIN    AND    THE    KIDNEYS.  243 

£  of  an  inch.  The  total  number  in  the  body  is  estimated  at 
about  2,500,000,  thus  making  the  entire  length  of  the  tubes 
devoted  to  the  secretion  of  sweat  about  10  miles. 

240.   Nature  and  Properties  of   Sweat.     The  sweat  is  a 

turbid,  saltish  fluid  with  a  feeble  but  characteristic  odor  due  to 
certain  volatile  fatty  acids.  Urea  is  always  present  in  small 
quantities,  and  its  proportion  may  be  largely  increased  when 
there  is  deficiency  of  elimination  by  the  kidneys.  Thus  it  is 
often  observed  that  the  sweat  is  more  abundant  when  the  kid- 
neys are  inactive,  and  the  reverse  is  true.  This  explains  the 
increased  excretion  of  the  kidneys  in  cold  weather.  Of  the 
inorganic  constituents  of  sweat,  common  salt  is  the  largest 
and  most  important.  Some  carbon  dioxid  passes  out  through 
the  skin,  but  not  more  than  -fa  as  much  as  escapes  by  the 
lungs. 

The  sweat  ordinarily  passes  off  as  vapor.  If  there  is  no 
obvious  perspiration  we  must  not  infer  that  the  skin  is  inactive, 
since  sweat  is  continually  passing  from  the  surface,  though 
often  it  may  not  be  apparent.  On  an  average  from  i£-  to  4 
pounds  of  sweat  are  eliminated  daily  from  the  skin  in  the  form 
of  vapor.  This  is  double  the  amount  excreted  by  the  lungs, 
and  averages  about  ^T  of  the  weight  of  the  body. 

The  visible  sweat,  or  sensible  perspiration,  becomes  abundant 
during  active  exercise,  after  copious  drinking  of  cold  water,  on 
taking  certain  drugs,  and  when  the  body  is  exposed  to  exces- 
sive warmth.  Forming  more  rapidly  than  it  evaporates  it  col- 
lects in  drops  on  the  surface.  The  disagreeable  sensations 
produced  by  humid  weather  result  from  the  fact  that  the 
atmosphere  is  so  loaded  with  vapor  that  the  moisture  of  the 
skin  is  slowly  removed  by  evaporation. 

Experiment  124.  Study  the  openings  of  the  sweat  glands  with  the  aid 
of  a  strong  magnifying  glass.  They  are  conveniently  examined  on  the 
palms. 


244  PRACTICAL  PHYSIOLOGY. 

A  man's  weight  may  be  considerably  reduced  within  a  short 
time  by  loss  through  the  perspiration  alone.  This  may  explain 
to  some  extent  the  weakening  effect  of  profuse  perspiration,  as 
from  night  sweats  of  consumption,  convalescence  from  typhoid 
fever,  or  the  artificial  sweating  from  taking  certain  drugs. 

241.  The  Skin  as  a  Regulator  of  the  Temperature  of  the 
Body.     We  thus  learn  that  the  skin  covers  and  protects  the 
more  delicate  structures  beneath  it  ;  and  that  it  also  serves  as 
an  important  organ  of  excretion.     By  means  of  the  sweat  the 
skin  performs  a  third  and  a  most  important  function,  viz.,  that 
of  regulating  the  temperature  of  the  body. 

The  blood-vessels  of  the  skin,  like  those  of  other  parts  of 
the  body,  are  under  the  control  of  the  nervous  system,  which 
regulates  their  diameter.  If  the  nervous  control  be  relaxed, 
the  blood-vessels  dilate,  more  blood  flows  through  them,  and 
more  material  is  brought  to  the  glands  of  the  skin  to  be  acted 
upon.  External  warmth  relaxes  the  skin  and  its  blood-vessels. 
There  results  an  increased  flow  of  blood  to  the  skin,  with  in- 
creased perspiration.  External  cold,  on  the  other  hand,  con- 
tracts the  skin  and  its  blood-vessels,  producing  a  diminished 
supply  of  blood  and  a  diminished  amount  of  sweat. 

Now,  it  is  a  law  of  physics  that  the  change  from  liquid  to 
vapor  involves  a  loss  of  heat.  A  few  drops  of  ether  or  of  any 
volatile  liquid  placed  on  the  skin,  produce  a  marked  sense  of 
coldness,  because  the  heat  necessary  to  change  the  liquid  into 
vapor  has  been  drawn  rapidly  from  the  skin.  This  principle 
holds  good  for  every  particle  of  sweat  that  reaches  the  mouth 
of  a  sweat  gland.  As  the  sweat  evaporates,  it  absorbs  a  cer- 
tain amount  of  heat,  and  cools  the  body  to  that  extent. 

242.  How  the  Action  of  the  Skin  may  be  Modified.     After 
profuse  sweating  we  feel  chilly  from  the  evaporation  of  a  large 
amount  of  moisture,  which  rapidly  cools  the  surface.     When 
the  weather  is  very  warm  the  evaporation  tends  to  prevent  the 


THE    SKIN    AND    THE    KIDNEYS. 


245 


bodily  temperature  from  rising.  On  the  other  hand,  if  the 
weather  be  cold,  much  less  sweat  is  produced,  the  loss  of  heat 
from  the  body  is  greatly  lessened,  and  its  temperature  pre- 
vented from  falling.  Thus  it  is  plain  why  medicine  is  given 
and  other  efforts  are  made  to  sweat  the  fever  patient.  The 
increased  activity  of  the  skin  helps  to  reduce  the  bodily  heat. 

The  sweat  glands  are  under  the  control  of  certain  nerve 
fibers  originating  in  the  spinal 
cord,  and  are  not  necessarily 
excited  to  action  by  an  in- 
creased flow  of  blood  through 
the  skin.  In  other  words,  the 
sweat  glands  may  be  stimulated 
to  increased  action  both  by  an 
increased  flow  of  blood,  and 
also  by  reflex  action  upon  the 
vaso-dilator  nerves  of  the  parts. 
These  two  agencies,  while  work- 
ing in  harmony  through  the 
vaso-dilators,  produce  phenom- 
ena which  are  essentially  inde- 
pendent of  each  other.  Thus 
a  strong  emotion,  like  fear,  may 
cause  a  profuse  sweat  to  break  out,  with  cold,  pallid  skin. 
During  a  fever  the  skin  may  be  hot,  and  its  vessels  full  of  blood, 
and  yet  there  may  be  no  perspiration. 

The  skin  may  have  important  uses  with  which  we  are  not 
yet  acquainted.  Death  ensues  when  the  heat  of  the  body  has 
been  reduced  to  about  70°  F.,  and  suppression  of  the  action  of 
-the  skin  always  produces  a  lowering  of  the  temperature.  Warm- 
blooded animals  usually  die  when  more  than  half  of  the  general 
surface  has  been  varnished.  Superficial  burns  which  involve 
a  large  part  of  the  surface  of  the  body,  generally  have  a  fatal 
result  due  to  shock. 


FIG.  103.  —  Papillae  of  the  Skin  of  the 
Palm  of  the  Hand. 

In  each  papilla  are  seen  vascular  loops  (dark 
lines)  running  up  from  the  vascular  net- 
work below;  the  tactile  corpuscles  with 
their  nerve  branches  (white  lines)  which 
supply  the  papillae. 


246 


PRACTICAL    PHYSIOLOGY. 


If  the  skin  be  covered  with  some  air-tight  substance  like  a 
coating  of  varnish,  its  functions  are  completely  arrested.  The 
bodily  heat  falls  very  rapidly.  Symptoms  of  blood-poisoning 
arise,  and  death  soon  ensues.  The  reason 
is  not  clearly  known,  unless  it  be  from  the 
sudden  retention  of  poisonous  exhalations. 

243.  The  Skin  and  the  Kidneys.   There 
is  a  close  relationship  between  the  skin  and 
the  kidneys,  as  both  excrete  organic  and 
saline  matter.     In  hot  weather,  or  in  con- 
ditions producing  great  activity  of  the  skin, 
the  amount  of  water  excreted  by  the  kid- 
neys is  diminished.     This  is  shown  in  the 
case  of  firemen,  stokers,  bakers,  and  others 
who  are  exposed  to  great  heat,  and  drink 
heavily  and  sweat  profusely,  but  do  not 
have  a  relative  increase  in  the  functions  of 
the  kidneys.     In  cool  weather,  when  the 
skin  is  less  active,  a  large  amount  of  water 
is  excreted  by  the  kidneys,  as  is  shown  by 
the  experience  of  those  who  drive  a  long 
distance  in  severe  weather,  or  who  have 
caught  a  sudden  cold. 

244.  Absorbent  Powers  of  the  Skin. 
The   skin    serves   to   some    extent   as   an 
organ   for   absorption.      It  is  capable  of 
absorbing  certain  substances  to  which  it  is 

freely  exposed.  Ointments  rubbed  in,  are  absorbed  by  the 
lymphatics  in  those  parts  where  the  skin  is  thin,  as  in  the  bend 
of  the  elbow  or  knee,  and  in  the  armpits.  Physicians  use  medi- 
cated ointments  in  this  way,  when  they  wish  to  secure  prompt 
and  efficient  results.  Feeble  infants  often  grow  more  vigorous 
by  having  their  skin  rubbed  vigorously  daily  with  olive  oil. 


FIG.  104.  —  Magnified 
View  of  a  Sweat  Gland 
with  its  Duct. 

The  convoluted  gland  is 
seen  surrounded  with  big 
fat -cells,  and  may  be 
traced  through  the  der- 
mis  to  its  outlet  in  the 
horny  layers  of  the  epi- 
dermis. 


THE    SKIN    AND    THE    KIDNEYS. 

A  slight  amount  of  water  is  absorbed  in  bathing.  Sailors 
deprived  of  fresh  water  have  been  able  to  allay  partially  their 
intense  thirst  by  soaking  their  clothing  in  salt  water.  The 
extent  to  which  absorption  occurs  through  the  healthy  skin  is, 
however,  quite  limited.  If  the  outer  skin  be  removed  from 
parts  of  the  body,  the  exposed  surface  absorbs  rapidly.  Vari- 
ous substances  may  thus  be  absorbed,  and  rapidly  passed  into 
the  blood.  When  the  physician  wishes  remedies  to  act  through 
the  skin,  he  sometimes  raises  a  small  blister,  and  dusts  over 
the  surface  some  drug,  a  fine  powder,  like  morphine. 

The  part  played  by  the  skin  as  an  organ  of  touch  will  be 
considered  in  sections  314  and  315. 

Experiment  125.  To  illustrate  the  sense  of  temperature.  Ask  the  person 
to  close  his  eyes.  Use  two  test  tubes,  one  filled  with  cold  and  the  other 
with  hot  water,  or  two  spoons,  one  hot  and  one  cold.  Apply  each  to 
different  parts  of  the  surface,  and  ask  the  person  whether  the  touching  body 
is  hot  or  cold.  Test  roughly  the  sensibility  of  different  parts  of  the  body 
with  cold  and  warm  metallic-pointed  rods. 

Experiment  126.  Touch  fur,  wood,  and  metal.  The  metal  feels  coldest, 
although  all  the  objects  are  at  the  same  temperature.  Why? 

Experiment  127.  Plunge  the  hand  into  water  at  about  97°  F.  One  ex- 
periences a  feeling  of  heat.  Then  plunge  it  into  water  at  about  86°  F. ;  at 
first  it  feels  cold,  because  heat  is  abstracted  from  the  hand.  Plunge  the 
other  hand  direct  into  water  at  86°  F.  without  previously  placing  it  in  water 
at  97°  F.,  —  it  will  feel  pleasantly  warm. 

Experiment  128.  To  illustrate  warm  and  cold  spots.  With  a  blunt  me- 
tallic point,  touch  different  parts  of  the  skin.  Certain  points  excite  the 
sensation  of  warmth,  others  of  cold,  although  the  temperatures  of  the  skin 
and  of  the  instrument  remain  constant. 

245.  Necessity  for  Personal  Cleanliness.  It  is  evident  that 
the  skin,  with  its  myriads  of  blood-vessels,  nerves,  and  sweat  and 
oil  glands,  is  an  exceedingly  complicated  and  important  struc- 
ture. The  surface  is  continually  casting  off  perspiration,  oily 
material,  and  dead  scales.  By  friction  and  regular  bathing  we 


248  PRACTICAL  PHYSIOLOGY. 

get  rid  of  these  waste  materials.  If  this  be  not  thoroughly 
done,  the  oily  secretion  holds  the  particles  of  waste  substances 
to  the  surface  of  the  body,  while  dust  and  dirt  collect,  and 
form  a  layer  upon  the  skin.  When  we  remember  that  this 
dirt  consists  of  a  great  variety  of  dust  particles,  poisonous 
matters,  and  sometimes  germs  of  disease,  we  may  well  be  im- 
pressed with  the  necessity  of  personal  cleanliness. 

This  layer  of  foreign  matter  on  the  skin  is  in  several  ways 
injurious  to  health.  It  clogs  the  pores  and  retards  perspira- 
tion, thus  checking  the  proper  action  of  the  skin  as  one  of  the 
chief  means  of  getting  rid  of  the  waste  matters  of  the  body. 
Hence  additional  work  is  thrown  upon  other  organs,  chiefly  the 
lungs  and  the  kidneys,  which  already  have  enough  to  do.  This 
extra  work  they  can  do  for  only  a  short  time.  Sooner  or  later 
they  become  disordered,  and  illness  follows.  Moreover,  as 
this  unwholesome  layer  is  a  fertile  soil  in  which  bacteria  may 
develop,  many  skin  diseases  may  result  from  this  neglect.  It 
is  also  highly  probable  that  germs  of  disease  thus  adherent  to 
the  skin  may  then  be  absorbed  into  the  system.  Parasitic 
skin  diseases  are  thus  greatly  favored  by  the  presence  of  an 
unclean  skin.  It  is  also  a  fact  that  uncleanly  people  are  more 
liable  to  take  cold  than  those  who  bathe  often. 

The  importance  of  cleanliness  would  thus  seem  too  apparent 
to  need  special  mention,  were  it  not  that  the  habit  is  so  much 
neglected.  The  old  and  excellent  definition  that  dirt  is  suitable 
matter,  but  in  the  wrong  place,  suggests  that  the  place  should 
be  changed.  This  can  be  done  only  by  regular  habits  of  per- 
sonal cleanliness,  not  only  of  the  skin,  the  hair,  the  teeth,  the 
nails,  and  the  clothing,  but  also  by  the  rigid  observance  of 
a  proper  system  in  daily  living. 

246.  Baths  and  Bathing.  In  bathing  we  have  two  distinct 
objects  in  view,  —  to  keep  the  skin  clean  and  to  impart  vigor. 
These  are  closely  related,  for  to  remove  from  the  body  worn- 


THE    SKIN    AND    THE    KIDNEYS.  249 

out  material,  which  tends  to  injure  it,  is  a  direct  means  of  giv- 
ing vigor  to  all  the  tissues.  Thus  a  cold  bath  acts  upon  the 
nervous  system,  and  calls  out,  in  response  to  the  temporary 
abstraction  of  heat,  a  freer  play  of  the  general  vital  powers. 
Bathing  is  so  useful,  both  locally  and  constitutionally,  that  it 
should  be  practiced  to  such  an  extent  as  experience  proves  to 
be  beneficial.  For  the  general  surface,  the  use  of  hot  water 
once  a  week  fulfills  the  demands  of  cleanliness,  unless  in 
special  occupations.  Whether  we  should  bathe  in  hot  or  cold 
water  depends  upon  circumstances.  Most  per- 
sons, especially  the  young  and  vigorous,  soon 
become  accustomed  to  cool,  and  even  cold  water 
baths,  at  all  seasons  of  the  year. 

The  hot  bath  should  be  taken  at  night  before 
going  to  bed,  as  in  the  morning  there  is  usually 
more  risk  of  taking  cold.  The  body  is  readily 
chilled,  if  exposed  to  cold  when  the  blood-vessels  FlG'  "S—  Ejf 

thelial  Cells 

of  the  skin  have  been   relaxed  by  heat.      Hot      from  the  Sweat 
baths,   besides    their   use   for   the   purposes   of      Glands, 
cleanliness,  have  a  sedative  influence  upon  the  The  ceils  are  very 
nervous  system,  tending  to  allay  restlessness  and 
weariness.      They    are    excellent    after    severe    mentary 
physical  or  mental  work,  and  give  a  feeling  of 
restful  comfort  like  that  of  sleep. 

Cold  baths  are  less  cleansing  than  hot,  but  serve  as  an  ex- 
cellent tonic  and  stimulant  to  the  bodily  functions.  The  best 
and  most  convenient  time  for  a  cold  bath  is  in  the  morning, 
immediately  after  rising.  To  the  healthy  and  vigorous,  it  is,  if 
taken  at  this  time,  with  proper  precautions,  a  most  agreeable 
and  healthful  luxury.  The  sensation  of  chilliness  first  felt  is 
caused  by  the  contraction  of  the  skin  and  its  blood-vessels,  so 
that  the  blood  is  forced  back,  as  it  were,  into  the  deeper  parts 
of  the  body.  This  stimulates  the  nervous  system,  the  breath- 
ing becomes  quicker  and  deeper,  the  heart  beats  more  vigor- 


25O  PRACTICAL  PHYSIOLOGY. 

ously,  and,  as  a  consequence,  the  warm  blood  is  sent  back  to 
the  skin  with  increased  force.  This  is  known  as  the  stage  of 
reaction,  which  is  best  increased  by  friction  with  a  rough  towel. 
This  should  produce  the  pleasant  feeling  of  a  warm  glow  all 
over  the  body. 

A  cold  bath  which  is  not  followed  by  reaction  is  likely  to  do 
more  harm  than  good.  The  lack  of  this  reaction  may  be  due 
to  the  water  being  too  cold,  the  bath  too  prolonged,  or  to  the 
bather  being  in  a  low  condition  of  health.  In  brief,  the  ruddy 
glow  which  follows  a  cold  bath  is  the  main  secret  of  its  favor- 
able influence. 

The  temperature  of  the  water  should  be  adapted  to  the  age 
and  strength  of  the  bather.  The  young  and  robust  can  safely 
endure  cold  baths,  that  would  be  of  no  benefit  but  indeed  an 
injury  to  those  of  greater  age  or  of  less  vigorous  conditions  of 
health.  After  taking  a  bath  the  skin  should  be  rapidly  and 
vigorously  rubbed  dry  with  a  rough  towel,  and  the  clothing  at 
once  put  on. 

247.  Rules  and  Precautions  in  Bathing.  Bathing  in  cold 
water  should  not  be  indulged  in  after  severe  exercise  or  great 
fatigue,  whether  we  are  heated  or  not.  Serious  results  have 
ensued  from  cold  baths  when  the  body  is  in  a  state  of  exhaus- 
tion or  of  profuse  perspiration.  A  daily  cold  bath  when  the 
body  is  comfortably  warm,  is  a  safe  tonic  for  almost  all  persons 
during  the  summer  months,  and  tends  especially  to  restore  the 
appetite.  Cold  baths,  taken  regularly,  render  persons  who  are 
susceptible  to  colds  much  less  liable  to  them,  and  less  likely 
to  be  disturbed  by  sudden  changes  of  temperature.  Persons 
suffering  from  heart  disease  or  from  chronic  disease  of  any 
important  organ  should  not  indulge  in  frequent  cold  baths, 
except  by  medical  advice.  Owing  to  the  relaxing  nature  of 
hot  baths,  persons  with  weak  hearts  or  suffering  from  debility 
may  faint  while  taking  them. 


THE    SKIN    AND    THE    KIDNEYS. 


251 


Outdoor  bathing  should  not  be  taken  for  at  least  an  hour 
after  a  full  meal,  and  except  for  the  robust  it  is  not  prudent  to 
bathe  with  the  stomach  empty,  especially  before  breakfast.  It 
is  a  wise  rule,  in  outdoor  or  sea  bathing,  to  come  out  of  the 
water  as  soon  as  the  glow  of  reaction  is  felt.  It  is  often  advis- 
able not  to  apply  cold  water  very  freely  to  the  head.  Tepid  or 
even  hot  water  is  preferable,  especially  by  those  subject  to 
severe  mental  strain.  But  it  is  often 
a  source  of  great  relief  during  men- 
tal strain  to  bathe  the  face,  neck, 
and  chest  freely  at  bedtime  with 
cold  water.  It  often  proves  efficient 
at  night  in  calming  the  sleeplessness 
which  results  from  mental  labor. 

Hot  baths,  if  taken  at  bedtime, 
are  often  serviceable  in  preventing 
a  threatened  cold  or  cutting  it  short, 
the  patient  going  immediately  to 
bed,  with  extra  clothing  and  hot 
drinks.  The  free  perspiration  in- 
duced helps  to  break  up  the  cold. 

Salt  water  acts  more  as  a  stimu- 
lant to  the  skin  than  fresh  water. 
Salt-water  bathing  is  refreshing 
and  invigorating  for  those  who  are 
healthy,  but  the  bather  should  come 
out  of  the  water  the  moment  there 
is  the  slightest  feeling  of  chilliness. 
The  practice  of  bathing  in  salt 
water  more  than  once  a  day  is  unhealthful,  and  even  dangerous. 
Only  the  strongest  can  sustain  so  severe  a  tax  on  their  power 
of  endurance.  Sea  bathing  is  beneficial  in  many  ways  for 
children,  as  their  skin  reacts  well  after  it.  In  all  cases,  brisk 
rubbing  with  a  rough  towel  should  be  had  afterwards. 


FIG.  106.  —  Magnified  Section  of 
the  Lower  Portion  of  a  Hair 
and  Hair-Follicle. 

A,  membrane  of  the  hair-follicle,  cells 
with  nuclei  and  pigmentary  gran- 
ules; B,  external  lining  of  the  root 
sheath ;  C,  internal  lining  of  the 
root  sheath;  D,  cortical  or  fibrous 
portion  of  the  hair  shaft ;  E,  medul- 
lary portion  (pith)  of  shaft ;  F,  hair- 
bulb,  showing  its  development  from 
cells  from  A. 


PRACTICAL    PHYSIOLOGY. 

The  golden  rule  of  all  bathing  is  that  it  must  never  be  fol- 
lowed by  a  chill.  If  even  a  chilliness  occur  after  bathing,  it 
must  immediately  be  broken  up  by  some  appropriate  methods, 
as  lively  exercise,  brisk  friction,  hot  drinks,  and  the  application 
of  heat. 

Swimming  is  a  most  valuable  accomplishment,  combining 
bathing  and  exercise.  Bathing  of  the  feet  should  never  be 
neglected.  Cleanliness  pf  the  hair  is  also  another  matter 
requiring  strict  attention,  especially  in  children. 

248.  Care  of  the  Hair  and  Nails.     The  hair  brush  should  not  be 
too  stiff,  as  this  increases  the  tendency  towards  scurfiness  of  the 

head.  If,  however,  the  hair  is  brushed 
too  long  or  too  hard,  the  scalp  is  greatly 
stimulated,  and  an  increased  production  of 
scurf  may  result.  If  the  head  be  washed 
too  often  with  soap  its  natural  secretion  is 
checked,  and  the  scalp  becomes  dry  and 

scaly.     The  various  hair  pomades  are  as  a 

FIG.  107.  — Longitudinal  Sec-  » 

tion  of  a  Finger-Nail.  rule  undesirable  and  unnecessary. 

A,  last  phalanx  of  the  fingers;  B,        The  nails  should  be  kept  in  proper  con- 
true  skin  on  the  dorsal  surface    ditiori,  else  they  are  not  only  unsightly,  but 

of  the  finger;  C   epidermis ;  D,  serye  ^  ^  f  f   dj 

true  skin  ;    E,  bed  of  the  nail ;  ' 

F,  superficial  layer  of  the  nail;   The  nails  are  often  injured  by  too  much 

H,  true  skin  of  the  pulp  of  the   interference,  and  should  never  be  trimmed 

to  the  quick.     The  upper  surfaces  should 

on  no  account  be  scraped.     The  nail-brush  is  sufficient  to  cleanse 
them  without  impairing  their  smooth  and  polished  surfaces. 

249.  Use  of  Clothing.     The  chief  use  of  clothing,  from  a 
hygienic  point  of  view,  is  to  assist  in  keeping  the  body  at  a 
uniform  temperature.      It  also  serves  for  protection   against 
injury,  and  for  personal  adornment.     The  heat  of  the  body,  as 
we  have  learned,  is  normally  about  98^°  F,     This  varies  but 
slightly  in  health.     A  rise  of  temperature  of  more  than  one 
degree  is  a  symptom  of  disturbance.     The  normal  temperature 


THE    SKIN    AND    THE    KIDNEYS.  253 

does  not  vary  with  the  season.  In  summer  it  is  kept  down  by 
the  perspiration  and  its  rapid  evaporation.  In  winter  it  is 
maintained  by  more  active  oxidation,  by  extra  clothing,  and  by 
artificial  heat. 

The  whole  matter  of  clothing  is  modified  to  a  great  extent 
by  climatic  conditions  and  local  environments,  —  topics  which 
do  not  come  within  the  scope  of  this  book. 

250.  Material  Used  for  Clothing.  It  is  evident  that  if  clothing 
is  to  do  double  duty  in  preventing  the  loss  of  heat  by  radiation,  and 
in  protecting  us  from  the  hot  rays  of  the  sun,  some  material  must  be 
used  that  will  allow  the  passage  of  heat  in  either  direction.  The 
ideal  clothing  should  be  both  a  bad  conductor  and  a  radiator  of  heat. 
At  the  same  time  it  must  not  interfere  with  the  free  evaporation  of 
the  perspiration,  otherwise  chills  may  result  from  the  accumulation 
of  moisture  on  the  surface  of  the  body. 

Wool  is  a  bad  conductor,  and  should  be  worn  next  the  skin,  both 
in  summer  and  winter,  especially  in  variable  climates.  It  prevents, 
better  than  any  other  material,  the  loss  of  heat  from  the  body,  and 
allows  free  ventilation  and  evaporation.  Its  fibers  are  so  lightly 
woven  that  they  make  innumerable  meshes  enclosing  air,  which  is  one 
of  the  best  of  non-conductors. 

Silk  ranks  next  to  wool  in  warmth  and  porosity.  It  is  much  softer 
and  less  irritating  than  flannel  or  merino,  and  is  very  useful  for  sum- 
mer wear.  The  practical  objection  to  its  general  use  is  the  expense. 
Fur  ranks  with  wool  as  a  bad  conductor  of  heat  It  does  not,  how- 
ever, like  wool,  allow  of  free  evaporation.  Its  use  in  cold  countries 
is  universal,  but  in  milder  climates  it  is  not  much  worn. 

Cotton  and  linen  are  good  conductors  of  heat,  but  are  not  absorb- 
ents of  moisture,  and  should  not  be  worn  next  the  skin.  They  are, 
however,  very  durable  and  easily  cleansed.  As  an  intermediate 
clothing  they  may  be  worn  at  all  seasons,  especially  over  wool  or 
silk.  Waterproof  clothing  is  also  useful  as  a  protection,  but  should 
not  be  worn  a  longer  time  than  necessary,  as  it  shuts  in  the  perspira- 
tion, and  causes  a  sense  of  great  heat  and  discomfort. 

The  color  of  clothing  is  of  some  importance,  especially  if  exposed 
directly  to  the  sun's  rays.  The  best  reflectors,  such  as  white  and 


254  PRACTICAL    PHYSIOLOGY. 

light  gray  clothing,  absorb  comparatively  little  heat  and  are  the 
coolest,  while  black  or  dark-colored  materials,  being  poor  reflectors 
and  good  absorbents,  become  very  warm. 

251.  Suggestions  for  the  Use  of  Clothing.  Prudence  and 
good  sense  should  guide  us  in  the  spring,  in  changing  winter 
flannels  or  clothing  for  fabrics  of  lighter  weight.  With  the 
fickle  climate  in  most  sections  of  this  country,  there  are  great 
risks  of  severe  colds,  pneumonia,  and  other  pulmonary  diseases 
from  carelessness  or  neglect  in  this  matter.  A  change  from 
heavy  to  lighter  clothing  should  be  made  first  in  the  outer  gar- 
ments, the  underclothing  being  changed  very  cautiously. 

The  two  essentials  of  healthful  clothing  are  cleanliness  and 
dryness.  To  wear  garments  that  are  daily  being  soiled  by 
perspiration  and  other  cutaneous  excretions,  is  a  most  uncleanly 
and  unhealthful  practice.  Clothing,  especially  woolen  under- 
clothing, should  be  frequently  changed.  One  of  the  objections 
to  the  use  of  this  clothing  is  that  it  does  not  show  soiling  to 
the  same  extent  as  do  cotton  and  linen. 

Infectious  and  contagious  diseases  may  be  conveyed  by  the 
clothing.  Hence,  special  care  must  be  taken  that  all  clothing 
in  contact  with  sick  people  is  burned  or  properly  disinfected. 
Children  especially  are  susceptible  to  scarlet  fever,  diphtheria, 
and  measles,  and  the  greatest  care  must  be  exercised  to  pre- 
vent their  exposure  to  infection  through  the  clothing. 

We  should  never  sleep  in  a  damp  bed,  or  between  damp 
sheets.  The  vital  powers  are  enfeebled  during  sleep,  and  there 
is  always  risk  of  pneumonia  or  rheumatism.  The  practice  of 
sitting  with  wet  feet  and  damp  clothing  is  highly  injurious  to 
health.  The  surface  of  the  body  thus  chilled  may  be  small, 
yet  there  is  a  grave  risk  of  serious,  if  not  of  fatal,  disease.  No 
harm  may  be  done,  even  with  clothing  wet  with  water  or  damp 
with  perspiration,  so  long  as  exercise  is  maintained,  but  the 
failure  or  inability  to  change  into  dry  garments  as  soon  as  the 
body  is  at  rest  is  fraught  with  danger. 


THE  SKIN  AND  THE  KIDNEYS.  255 

Woolen  comforters,  scarfs,  and  fur  mufflers,  so  commonly 
worn  around  the  neck,  are  more  likely  to  produce  throat  trou- 
bles and  local  chill  than  to  have  any  useful  effect.  Harm 
ensues  from  the  fact  that  the  extra  covering  induces  local 
perspiration,  which  enfeebles  the  natural  defensive  power  of 
the  parts ;  and  when  the  warmer  covering  is  removed,  the  per- 
spiring surface  is  readily  chilled.  Those  who  never  bundle 
their  throats  are  least  liable  to  suffer  from  throat  ailments. 

252.   Ill  Effects  of  WearingTightly  Fitting  Clothing.    The 

injury  to  health  caused  by  tight  lacing,  when  carried  to  an 
extreme,  is  due  to  the  compression  and  displacement  of  vari- 
ous organs  by  the  pressure  exerted  on  them.  Thus  the  lungs 
and  the  heart  may  be  compressed,  causing  short  breath  on 
exertion,  palpitation  of  the  heart,  and  other  painful  and  danger- 
ous symptoms.  The  stomach,  the  liver,  and  other  abdominal 
organs  are  often  displaced,  causing  dyspepsia  and  all  its  atten- 
dant evils.  The  improper  use  of  corsets,  especially  by  young 
women,  is  injurious,  as  they  interfere  with  the  proper  develop- 
ment of  the  chest  and  abdominal  organs.  The  use  of  tight 
elastics  below  the  knee  is  often  injurious.  They  obstruct  the 
local  venous  circulation  and  are  a  fruitful  source  of  cold  feet 
and  of  enlarged  or  varicose  veins. 

Tightly  fitting  boots  and  shoes  often  cause  corns,  bunions, 
and  ingrowing  nails  ;  on  the  other  hand,  if  too  loosely  worn, 
they  cause  corns  from  friction.  Boots  too  narrow  in  front 
crowd  the  toes  together,  make  them  overlap,  and  render  walk- 
ing difficult  and  painful.  High-heeled  boots  throw  the  weight 
of  the  body  forwards,  so  that  the  body  rests  too  much  on  the 
toes  instead  of  on  the  heels,  as  it  should,  thus  placing  an  undue 
strain  upon  certain  groups  of  muscles  of  the  leg,  in  order  to 
maintain  the  balance,  while  other  groups  are  not  sufficiently 
exercised.  Locomotion  is  never  easy  and  graceful,  and  a  firm, 
even  tread  cannot  be  expected. 


256  PRACTICAL  PHYSIOLOGY. 

The  compression  of  the  scalp  by  a  tight-fitting  hat  interferes 
with  the  local  circulation,  and  may  cause  headaches,  neuralgia, 
or  baldness,  the  nutrition  of  the  hair-follicles  being  diminished 
by  the  impaired  circulation.  The  compression  of  the  chest  and 
abdomen  by  a  tight  belt  and  various  binders  interferes  with  the 
action  of  the  diaphragm,  —  the  most  important  muscle  of 
respiration. 

253.  Miscellaneous  Hints  on  the  Use  of  Clothing.  Chil- 
dren and  old  people  are  less  able  to  resist  the  extreme  changes 
of  temperature  than  are  adults  of  an  average  age.  Special  care 
should  be  taken  to  provide  children-with  woolen  underclothing, 
and  to  keep  them  warm  and  in  well-ventilated  rooms.  Neither 
the  chest  nor  limbs  of  young  children  should  be  unduly  ex- 
posed, as  is  often  done,  to  the  cold  blasts  of  winter  or  the 
fickle  weather  of  early  spring.  Very  young  children  should 
not  be  taken  out  in  extremely  cold  weather,  unless  quite  warmly 
clad  and  able  to  run  about.  The  absurd  notion  is  often  enter- 
tained that  children  should  be  hardened  by  exposure  to  the 
cold.  Judicious  "hardening"  means  ample  exposure  of  well- 
fed  and  well-clothed  children.  Exposure  of  children  not  thus 
cared  for  is  simple  cruelty.  The  many  sicknesses  of  children, 
especially  diseases  of  the  throat  and  lungs,  may  often  be  traced 
directly  to  gross  carelessness,  ignorance,  or  neglect  with  refer- 
ence to  undue  exposure.  The  delicate  feet  of  children  should 
not  be  injured  by  wearing  ill-fitting  or  clumsy  boots  or  shoes. 
Many  deformities  of  the  feet,  which  cause  much  vexation  and 
trouble  in  after  years,  are  acquired  in  early  life. 

No  one  should  sleep  in  any  of  the  clothes  worn  during  the 
day,  not  even  in  the  same  underclothing.  All  bed  clothing 
should  be  properly  aired,  by  free  exposure  to  the  light  and  air 
every  morning.  Never  wear  wet  or  damp  clothing  one  moment 
longer  than  necessary.  After  it  is  removed  rub  the  body  thor- 
oughly, put  on  at  once  dry,  warm  clothing,  and  then  exercise 


THE    SKIN    AND    THE    KIDNEYS. 

vigorously  for  a  few  minutes,  until  a  genial  glow  is  felt.  .  Neg- 
lect of  these  precautions  often  results  in  rheumatism,  neuralgia, 
and  diseases  of  the  chest,  especially  among  delicate  people  and 
young  women. 

Pupils  should  not  be  allowed  to  sit  in  the  schoolroom  with 
any  outer  garments  on.  A  person  who  has  become  heated  in 
a  warm  room  should  not  expose  himself  to  cold  without  extra 
clothing.  We  must  not  be  in  a  hurry  to  put  on  heavy  clothes 
for  winter,  but  having  once  worn  them,  they  must  not  be  left 
off  until  milder  weather  renders  the  change  safe.  The  cheaper 
articles  of  clothing  are  often  dyed  with  lead  or  arsenic. 
Hence  such  garments,  like  stockings  and  colored  underclothing, 
worn  next  the  skin  have  been  known  to  produce  severe  symp- 
toms of  poisoning.  As  a  precaution,  all  such  articles  should  be 
carefully  washed  and  thoroughly  rinsed  before  they  are  worn. 

THE   KIDNEYS. 

254.  The  Kidneys.  The  kidneys  are  two  important  organs 
in  the  abdomen,  one  on  each  side  of  the  spine.  They  are  of  a 
reddish-brown  color,  and  are  enveloped  by  a  transparent  cap- 
sule made  up  of  a  fold  of  the  peritoneum.  Embedded  in  fat, 
the  kidneys  lie  between  the  upper  lumbar  vertebrae,  and  the 
crest  of  the  hip  bone.  The  liver  is  above  the  right  kidney, 
and  the  spleen  above  the  left,  while  both  lie  close  against  the 
rear  wall  of  the  abdomen,  with  the  intestines  in  front  of  them. 
The  human  kidneys,  though  somewhat  larger,  are  exactly  of 
the  same  shape,  color,  and  general  appearance  as  those  of  the 
sheep,  so  commonly  seen  in  the  markets. 

The  kidneys  are  about  four  inches  long,  two  inches  across,  one 
inch  thick,  and  weigh  from  4^  to  5^  ounces  each.  The  hollow 
or  concave  side  of  the  kidneys  is  turned  inwards,  and  the  deep 
fissure  of  this  side,  known  as  the  hilus,  widens  out  to  form  the 
pelvis.  Through  the  hilus  the  renal  artery  passes  into  each 


258 


PRACTICAL    PHYSIOLOGY. 


kidney,  and  from  each  hilus  passes  outwards  the  renal  vein,  a 
branch  of  the  inferior  vena  cava. 

A  tube,  called  the  ureter,  passes  out  from  the  concave  bor- 
der of  each  kidney,  turns  downwards,  and  enters  the  bladder 

in  the  basin  of  the  pelvis. 
This  tube  is  from  12  to  14 
inches  long,  about  as  large 
as  a  goose  quill,  and  conveys 
the  secretion  of  the  kidneys 
to  the  bladder. 

255.  Structure  of  the 
Kidneys.  The  pelvis  is  sur- 
rounded by  reddish  cones, 
about  twelve  in  number,  pro- 
jecting into  it,  called  the 
pyramids  of  Malpighi.  The 
apices  of  these  cones,  known 
as  the  papilla,  are  crowded 
with  minute  openings,  the 
mouths  of  the  uriniferous 

tubules,  which  form  the  sub- 
FIG.  108— Vertical  Section  of  the  Kidney.  gtance  Q£  the  kidney>  These 
A,  pyramids  of  Malpighi ;  B,  apices,  or  papillae,  ,.  .,  ,  .  ,  ,  ,, 

of  the  pyramids,  surrounded  by  subdivisions  of  ll6  Parallel  in  the  medullary 
the  pelvis  known  as  cups  or  calices ;  C,  pelvis  or  Central  Structure,  but  On 
of  the  kidney :  D,  upper  end  of  ureter.  ,  .  ,  , 

reaching  the  cortical  or  outer 

layer,  they  wind  about  and  interlace,  ending,  at  last,  in  dilated 
closed  sacs  called  Malpighian  capsules. 

256.  Function  of  the  Kidneys.  The  Malpighian  capsules 
are  really  the  beginning  of  the  tubules,  for  here  the  work  of 
excretion  begins.  The  thin  wall  of  the  capillaries  within  each 
capsule  separates  the  blood  from  the  cavity  of  the  tubule.  The 
blood-pressure  on  the  delicate  capillary  walls  causes  the  exuda- 
tion of  the  watery  portions  of  the  blood  through  the  cell  walls 


THE  SKIN  AND  THE  KIDNEYS.  259 

into  the  capsule.  The  epithelial  cell  membrane  allows  the  water 
of  the  blood  with  certain  salts  in  solution  to  pass,  but  rejects  the 
albumen.  From  the  capsules,  the  excretion  passes  through  the 
tubules  into  the  pelvis,  and  on  through  the  ureters  to  the  bladder. 
But  the  "delicate  epithelial  walls  of  the  tubules  through  which  it 
passes  permit  the  inflow  of  urea  and  other  waste  products  from 
the  surrounding  capillaries.  By  this  twofold  process  are  separ- 
ated from  the  blood  the  fluid  portions  of  the  renal  secretion 
with  soluble  salts,  and  the  urea  with  other  waste  material. 

257.   How  the  Action  of  the  Kidneys  may  be  Modified.     The 

action  of  the  kidneys  is  subject  to  very  marked  and  sudden  modifica- 
tions, especially  those  operating  through  the  nervous  system.  Thus 
whatever  raises  the  blood-pressure  in  the  capillaries  of  the  capsules, 
will  increase  the  quantity  of  fluid  filtering  through  them.  That  is,  the 
watery  portion  of  the  secretion  will  be  increased  without  necessarily 
adding  to  its  solids.  So  anything  which  lowers  the  blood-pressure 
will  diminish  the  watery  portion  of  the  secretion,  that  is,  the  secre- 
tion will  be  scanty,  but  concentrated. 

The  Renal  Secretion.  —  The  function  of  the  kidneys  is  to  secrete  a  fluid  com- 
monly known  as  the  urine.  The  average  quantity  passed  in  24  hours  by  an  adult 
varies  from  40  to  60  fluid  ounces.  Normal  urine  consists  of  about  96  per  cent 
of  water  and  4  per  cent  of  solids.  The  latter  consist  chiefly  of  certain  nitrogenous 
substances  known  as  urea  and  uric  acid,  a  considerable  quantity  of  mineral  salts, 
and  some  coloring  matter.  Urea,  the  most  important  and  most  abundant  constit- 
uent of  urine,  contains  the  four  elements,  but  nitrogen  forms  one-half  its  weight. 
While,  therefore,  the  lungs  expel  carbon  dioxid  chiefly,  the  kidneys  expel  nitrogen. 
Both  of  these  substances  express  the  result  of  oxidations  going  on  in  the- body. 
The  urea  and  uric  acids  represent  the  final  result  of  the  breaking  down  in  the  body 
of  nitrogenous  substances,  of  which  albumen  is  the  type. 

Unusual  constituents  of  the  urine  are  albumen,  sugar,  and  bile.  When  albumen 
is  present  in  urine,  it  often  indicates  some  disease  of  the  kidneys,  to  which  the 
term  albuminuria  or  Bright's  Disease  is  applied.  The  presence  of  grape  sugar  or 
glucose  indicates  the  disease  known  as  diabetes.  Bile  is  another  unusual  constituent 
of  the  urine,  appearing  \VL  jaundice. 

The  bladder  is  situated  in  the  pelvic  cavity  or  in  the  lowest  part  of  the  abdomen. 
When  full,  the  bladder  is  pear-shaped ;  when  empty,  it  is  collapsed  and  lies  low  in 
the  pelvis.  The  functions  of  the  bladder  are  to  collect  and  retain  the  urine,  which 
has  reached  it  drop  by  drop  from  the  kidneys  through  the  ureters,  until  a  certain 
quantity  accumulates,  and  then  to  expel  it  from  the  body. 


260 


PRACTICAL    PHYSIOLOGY. 


In  the  kidneys,  as  elsewhere,  the  vaso-motor  nerves  are  distributed 
to  the  walls  of  the  blood-vessels,  and  modify  the  quantity  and  the 
pressure  of  blood  in  these  organs.  Thus,  some  strong  emotion,  like 


FIG.  109.  —  Vertical  Section  of  the  Back.    (Showing  kidneys  in  situ  and  the 

relative  position  of  adjacent  organs  and  vessels.)      [Posterior  view.] 
A,  i2th  dorsal  vertebra;    B,  diaphragm;   C,  receptaculum  chyli;    D,  small  intestines. 

fear  or  undue  p.nxiety,  increases  the  blood-pressure,  drives  more  blood 
to  the  kidneys,  and  causes  a  larger  flow  of  watery  secretion.  When 
the  atmosphere  is  hot,  there  is  a  relaxation  of  the  vessels  of  the  skin, 


THE  SKIN  AND  THE  KIDNEYS.  26 1 

with  a  more  than  ordinary  flow  of  blood,  which  is  thus  withdrawn 
from  the  deeper  organs.  The  blood-pressure  in  the  kidneys  is  not 
only  diminished,  but  the  total  quantity  passing  through  them  in  a 
given  time  is  much  lessened.  As  a  result,  the  secretion  of  the  kid- 
neys is  scanty,  but  it  contains  an  unusual  percentage  of  solids. 

When  the  atmosphere  is  cold,  the  reverse  is  true.  The  cutaneous 
vessels  contract,  the  blood  is  driven  to  the  deeper  organs  with  increased 
pressure,  and  there  is  a  less  amount  of  sweat,  but  an  increased  renal 
secretion,  containing  a  smaller  proportion  of  solids.  Certain  d~ugs  have 
the  power  of  increasing  or  diminishing  the  renal  secretion.  As  the 
waste  matters  eliminated  by  the  kidneys  are  being  constantly  produced 
in  the  tissues,  the  action  of  the  renal  organs  is  continuous,  in  marked 
contrast  with  the  intermittent  flow  of  most  of  the  secretions  proper,  as 
distinguished  from  the  excretions. 

258.   Effects  of  Alcoholic  Drinks  upon  the  Kidneys.     The 

kidneys  differ  from  some  of  the  other  organs  in  this :  those 
ean  rest  a  while  without  any  harm  to  themselves,  or  to  the 
body.  We  can  keep  the  eyes  closed  for  a  few  days,  if  neces- 
sary, without  injury,  and  in  fact  often  with  benefit ;  or,  we  can 
abstain  from  food  for  some  days,  if  need  be,  and  let  the  stomach 
rest.  But  the  kidneys  cannot,  with  safety,  cease  their  work. 
Their  duty  in  ridding  the  blood  of  waste  products,  and  of  any 
foreign  or  poisonous  material  introduced,  must  be  done  not 
only  faithfully,  but  continually,  or  the  whole  body  at  once  suffers 
from  the  evil  effects  of  the  retained  waste  matters. 

This  vital  fact  is  the  key  to  the  injurious  results  developed 
in  the  kidneys  by  the  use  of  alcoholic  drinks.  These  two 
organs  have  large  blood-vessels  conveying  full  amounts  of 
blood  to  and  from  their  structures,  and  they  feel  very  quickly 
the  presence  of  alcohol.  Alcoholic  liquors  excite  and  irritate 
the  delicate  renal  membranes,  and  speedily  disturb  and  event- 
ually destroy  their  capacity  to  excrete  the  proper  materials 
from  the  blood. 

The    continued   congestion  of  the   minute   structure   of  the 


262  PRACTICAL    PHYSIOLOGY. 

kidney  cuts  off  the  needed  nutrition  of  the  organ,  and  forms 
the  primary  step  in  the  series  of  disasters.  Sometimes  from 
this  continued  irritation,  with  the  resulting  inflammation,  and 
sometimes  from  change  of  structure  of  the  kidney  by  fatty 
degeneration,  comes  the  failure  to  perform  its  proper  function. 
Then,  with  this  two-edged  sword  of  disaster,  the  urea,  which 
becomes  a  poisonous  element,  and  should  be  removed,  is  re- 
tained in  the  system,  while  the  albumen,  which  is  essential  to 
healthy  blood,  is  filtered  away  through  the  diseased  kidney. 

259.  Alcoholic  Liquors  as  a  Cause  of  Bright's  Disease. 
The  unfortunate  presence  of  albumen  in  the  urine  is  often  a 
symptom  of  that  insidious  and  fatal  malady  known  as  albumi- 
nuria  or  Bright's  disease,  often  accompanied  with  dropsy  and 
convulsions.  One  of  the  most  constant  causes  of  this  disease 
is  the  use  of  intoxicants.  It  is  not  at  all  necessary  to  this  fatal 
result  that  a  person  be  a  heavy  drinker.  Steady,  moderate 
drinking  will  often  accomplish  the  work.  Kidney  diseases 
produced  by  alcoholic  drinks,  are  less  responsive  to  medical 
treatment  and  more  fatal  than  those  arising  from  any  other 
known  cause.1 

Experiment  129.  Obtain  a  sheep's  kidney  in  good  order.  Observe  that 
its  shape  is  something  like  that  of  a  bean,  and  note  that  the  concave  part 
(hilus),  when  in  its  normal  position,  is  turned  towards  the  backbone.  Notice 
that  all  the  vessels  leave  and  enter  the  kidney  at  the  hilus.  Observe  a 
small  thick-walled  vessel  with  open  mouth  from  wrhich  may  be  pressed  a 
few  drops  of  blood.  This  is  the  renal  artery.  Pass  a  bristle  down  it. 
With  the  forceps,  or  even  with  a  penknife,  lift  from  the  kidney  the  fine 
membrane  enclosing  it.  This  is  the  kidney  capsule. 

Divide  the  kidney  in  halves  by  a  section  from  its  outer  to  near  its  inner 
border.  Do  not  cut  directly  through  the  hilus.  Note  on  the  cut  surfaces, 
on  the  outer  side,  the  darker  cortical  portion,  and  on  the  inner  side,  the 
smooth,  pale,  medullary  portion.  Note  also  the  pyramids  of  Malpighi. 

1  "  The  relation  to  Bright's  Disease  is  not  so  clearly  made  out  as  is  assumed  by 
some  writers,  though  I  must  confess  to  myself  sharing  the  popular  belief  that  alcohol 
is  one  among  its  most  important  factors." —  ROBERT  T.  EDES,  M.D, 


CHAPTER   X. 
THE  NERVOUS   SYSTEM. 

260.  General  View  of  the  Nervous  System.  Thus  far  we 
have  learned  something  of  the  various  organs  and  the  manner 
in  which  they  do  their  work.  Regarding  our  bodily  structure 
as  a  kind  of  living  machine,  we  have  studied  its  various  parts, 
and  found  that  each  is  designed  to  perform  some  special  work 
essential  to  the  well-being  of  the  whole.  As  yet  we  have 
learned  of  no  means  by  which  these  organs  are  enabled  to  adjust 
their  activities  to  the  needs  of  other  tissues  and  other  organs. 
We  are  now  prepared  to  study  a  higher,  a  more  wonderful  and 
complex  agency,  —  the  nervous  system,  the  master  tissue, 
which  controls,  regulates,  and  directs  every  other  tissue  of  the 
human  body. 

The  nervous  system,  in  its  properties  and  mode  of  action, 
is  distinct  from  all  the  other  systems  and  organs,  and  it  shares 
with  no  other  organ  or  tissue  the  power  to  do  its  special  work. 
It  is  the  medium  through  which  all  impressions  are  received. 
It  connects  all  the  parts  of  the  body  into  an  organism  in  which 
each  acts  in  harmony  with  every  other  part  for  the  good  of  the 
whole.  It  animates  and  governs  all  movements,  voluntary  or 
involuntary,  —  secretion,  excretion,  nutrition  ;  in  fact  all  the 
processes  of  organic  life  are  subject  to  its  regulating  power. 
The  different  organs  of  the  body  are  united  by  a  common 
sympathy  which  regulates  their  action  :  this  harmonious  result 
is  secured  by  means  of  the  nervous  system. 

This  system,  in  certain  of  its  parts,  receives  impressions,  and 
generates  a  force  peculiar  to  itself.  We  shall  learn  that  there 
can  be  no  physical  communication  between  or  coordination  of 


264  PRACTICAL  PHYSIOLOGY. 

the  various  parts  of  organs,  or  harmonious  acts  for  a  desired 
result,  without  the  nerves.  General  impressions,  as  in  ordinary 
sensation,  or  special  impressions,  as  in  sight,  smell,  taste,  or 
hearing,  —  every  instinct,  every  act  of  the  will,  and  every  thought 
are  possible  only  through  the  action  of  the  nerve  centers. 

261.  Nerve  Cells.  However  complicated  the  structure  of 
nerve  tissue  in  man  seems  to  be,  it  is  found  to  consist  of  only 
two  different  elements,  nerve  cells  and  nerve  fibers.  These 
are  associated  and  combined  in  many  ways.  They 
are  arranged  in  distinct  masses  called  nerve  cen- 
ters, or  in  the  form  of  cords  known  as  nerves. 
The  former  are  made  up  of  nerve  fibers ;  the  latter 
of  both  cells  and  fibers. 

Nerve  cells,  which  may  be  regarded  as  the  cen- 
tral organs  of  the  nerve  fibers,  consist  of  masses  of 
cell  protoplasm,  with  a  large  nucleus  and  nudeolus. 
F  They  bear  a  general  resemblance  to  other  cells,  but 

Nerve  Cells    varv  rnuch  in  size  and  shape.     Nerve  cells  grow, 
from  the      become  active,  and  die,  as  do  other  cells.     A  num- 
'   ber  of  processes  branch  off  from  them,  some  cells 
giving  one  or  two,  others  many.     The  various  kinds  of  nerve 
cells  differ  much  in  the  shape  and  number  of  processes.     One 
of  the  processes  is  a  strand  which  becomes  continuous  with  the 
axis  cylinder  of  the  nerve  fibers ;  that  is,  the  axis  cylinders  of 
all  nerve  fibers  are  joined  in  one  place  or  another  with  at  least 
one  cell. 

Each  part  of  this  system  has  its  own  characteristic  cell. 
Thus  we  have  in  the  spinal  cord  the  large,  irregular  cells  with 
many  processes,  and  in  the  brain  proper  the  three-sided  cells 
with  a  process  jutting  out  from  each  corner.  So  characteristic 
are  these  forms  of  cells,  that  any  particular  part  of  nerve  struc- 
ture may  be  identified  by  the  kind  of  cells  seen  under  the 
microscope.  Nerve  cells  and  nerve  fibers  are  often  arranged  in 


THE    NERVOUS    SYSTEM.  265 

groups,  the  various  cells  of  the  groups  communicating  with  one 
another.  This  clustered  arrangement  is  called  a  nerve  center. 

262.  Nerve  Fibers.  The  nerve  fibers,  the  essential  ele- 
ments of  the  nerves,  somewhat  resemble  tubes  filled  with  a 
clear,  jelly-like  substance.  They  consist  of  a  rod,  or  central 
core,  continuous  throughout  the  whole  length  of  the  nerve, 
called  the  axis  cylinder.  This  core  is  surrounded  by  the 
white  substance  of  Schwann,  or 
medullary  sheath,  which  gives 
the  nerve  its  characteristic  ivory- 
white  appearance.  The  whole 
is  enclosed  in  a  thin,  delicate 
sheath,  known  as  neurilemma. 

The  axis  cylinder  generally 
passes  without  any  break  from 
the  nerve  centers  to  the  end  of  FlG" '»— Nerve  Cells  from  the  Gray 

Matter  of  the  Brain. 

the  fibers.1      The  outer  sheath 

(neurilemma)  is  also  continuous  throughout  the  length  of  the 
fibers.  The  medullary  sheath,  on  the  other  hand,  is  broken 
at  intervals  of  about  ^  of  an  inch,  and  at  the  same  intervals 
nuclei  are  found  along  the  fiber,  around  each  of  which  is  a 
minute  protoplasmic  mass.  Between  each  pair  of  nuclei  the 
sheath  is  interrupted.  This  point  is  known  as  the  node  of 
Ranvier. 

Some  nerve  fibers  have  no  inner  sheath  (medullary),  the 
outer  alone  protecting  the  axis  cylinder.  These  are  known  as 
the  non-medullary  fibers.  They  are  gray,  while  the  ordinary 
medullary  fibers  are  white  in  appearance.  The  white  nerve  fi- 
bers form  the  white  part  of  the  brain  and  of  the  spinal  cord,  and 
the  greater  part  of  the  cerebro-spinal  nerves.  The  gray  fibers 

1  Thus  the  fibers  which  pass  out  from  the  sacral  plexus  in  the  loins,  and  extend  by 
means  of  the  great  sciatic  nerve  and  its  branches  to  the  ends  of  the  toes,  may  be 
more  than  a  yard  long. 


266 


PRACTICAL    PHYSIOLOGY. 


occur  chiefly  in  branches  from  the  sympathetic  ganglia,  though 
found  to  some  extent  in  the  nerves  of  the  cerebro-spinal  system. 
In  a  general  way,  the  nerve  fibers  resemble  an  electric  cable 
wire  with  its  central  rod  of  copper,  and  its  outer  non-conduct- 
ing layer  of  silk  or  gutta-percha.  Like  the  copper  rod,  the 
axis  cylinder  along  which  the  nerve  im- 
pulse travels  is  the  essential  part  of  a 
nerve  fiber.  In  a  cut  nerve  this  cylinder 
projects  like  the  wick  of  a  candle.  It  is 
really  the  continuation  of  a  process  of 
a  nerve  cell.  Thus  the  nerve  cells  and 
nerve  fibers  are  related,  in  that  the  proc- 
ess of  one  is  the  axis  cylinder  and 
essential  part  of  the  other. 

It'-.^l  The  separate  microscopic   threads   or 

Jll          fibers,  bound  together  in  cords  of  vari- 
1  I  able  size,  form  the  nerves.    Each  strand 

llfjjll  I  IS]          or  cord  is  surrounded  and  protected  by 

its  own  sheath  of  connective  tissue,  made 
up  of  nerves.  According  to  its  size  a 
nerve  may  have  one  or  many  of  these 
strands.  The  whole  nerve,  not  unlike  a 
minute  tendon  in  appearance,  is  covered 
by  a  dense  sheath  of  fibrous  tissue,  in 
which  the  blood-vessels  and  lymphatics 
are  distributed  to  the  nerve  fibers. 


FIG.  ii2.— Medullated 
Nerve  Fibers. 

A,  a  medullated  nerve  fiber, 
showing  the  subdivision  of 
the  medullary  sheath  into 
cylindrical  sections  imbri- 
cated with  their  ends ;  a 
nerve  corpuscle  with  an 
oval  nucleus  is  seen  be- 
tween the  neurilemma  and 
the  medullary  sheath.  B,  a 
medullated  nerve  fiber  at 
a  node  or  constriction  of 
Ranvier;  the  axis  cylinder 
passes  uninterruptedly  from 
one  segment  into  the  other, 
but  the  medullary  sheath  is 
interrupted. 


263.  The  Functions  of  the  Nerve 
Cells  and  Nerve  Fibers.  The  nerve 
cells  are  a  highly  active  mass  of  living 
material.  They  find  their  nourishment 
in  the  blood,  which  is  supplied  to  them 
in  abundance.  The  blood  not  only  serves  as  nourishment,  but 
also  supplies  new  material,  as  it  were,  for  the  cells  to  work 


THE    NERVOUS    SYSTEM. 


267 


over  for  their  own  force  or  energy.  Thus  we  may  think  of  the 
nerve  cells  as  a  sort  of  a  miniature  manufactory,  deriving  their 
material  from  the  blood,  and  developing  from  it  nervous  energy. 

The  nerve  fibers,  on  the  other  hand,  are 
conductors  of  nervous  energy.  They  fur- 
nish a  pathway  along  which  the  nerve 
energy  generated  by  the  cells  may  travel. 
Made  up  as  they  are  of  living  nerve  sub- 
stance, the  fibers  can  also  generate  energy, 
yet  it  is  their  special  function  to  conduct 
influences  to  and  from  the  cells. 


264.  The  Nervous  System  Compared  to  a 
Telegraphic  System.  In  men  and  other  highly 
organized  animals,  nerves  are  found  in  nearly 
every  tissue  and  organ  of  the  body.  They 
penetrate  the  most  minute  muscular  fibers ; 


FIG.  1 13 .  —  Non-  Medul- 

lated  Fibers. 
,         j     .       , ,  c  Two  nerve  fibers,  showing 

glands,   and   are  found  in  the   coats  of  even      the  nodes  or  constrictions 


they  are  closely  connected  with  the  cells  of  the 


of  Ranvier  and  the  axis 
cylinder.  The  medullary 
sheath  has  been  dissolved 
away.  The  deeply  stained 
oblong  nuclei  indicate  the 
nerve  corpuscles  within 
the  neurilemma. 


the  smallest  blood-vessels.     They  are  among 

the  chief  factors  of  the  structure  of  the  sense 

organs,   and  ramify  through  the  skin.     Thus 

the   nervous  system    is  the  system  of   organs 

through  the  functions  of  which  we  are  brought 

into  relation  with  the  world  around  us.     When 

we  hear,  our  ears  are  bringing  us  into  relation  with  the  outer  world. 

So  sight  opens  up  to  us  another  gateway  of  knowledge. 

It  will  help  us  the  better  to  understand  the  complicated  functions 
of  the  nervous  system,  if  we  compare'  it  to  a  telegraph  line.  The 
brain  is  the  main  office,  and  the  multitudes  of  nerve  fibers  branching 
off  to  all  parts  of  the  body  are  the  wires.  By  means  of  these,  nerve 
messages  are  constantly  being  sent  to  the  brain  to  inform  it  of  what 
is  going  on  in  various  parts  of  the  body,  and  asking  what  is  to  be 
done  in  each  case.  The  brain,  on  receiving  the  intelligence,  at  once 
sends  back  the  required  instructions.  Countless  messages  are  sent 
to  and  fro  with  unerring  accuracy  and  marvelous  rapidity. 


268  PRACTICAL    PHYSIOLOGY. 

Thus,  when  we  accidentally  pick  up  something  hot,  it  is  instantly 
dropped.  A  nerve  impulse  passes  from  the  nerves  of  touch  in  the 
fingers  to  the  brain,  which  at  once  hurries  off  its  order  along  another 
set  of  nerves  for  the  hand  to  drop  the  burning  object.  These  exam- 
ples, so  common  in  daily  life,  may  be  multiplied  to  any  extent. 
Almost  every  voluntary  act  we  perform  is  executed  under  the  direc- 
tion of  the  nervous  system,  although  the  time  occupied  is  so  small 
that  it  is  beyond  our  power  to  estimate  it.  The  very  frequency  with 
which  the  nerves  act  tends  to  make  us  forget  their  beneficent  work. 

265.  Divisions  of  the  Nervous  System.     This  system  in 
man  consists  of  two  great  divisions.     The  first  is  the  great 
nerve  center  of  the  body,  the  cerebro-spinal  system,  which 
rules   the  organs  of   animal    life.      This  includes  the   brain, 
the  spinal  cord,  and  the  cerebro-spinal  nerves.     Nerves  are 
given  off  from  the  brain  and  the  cord,  and  form  the  mediums 
of  communication  between  the  external  parts  of  the  body,  the 
muscles  or  the  sense  organs,  and  the  brain. 

The  second  part  is  the  sympathetic  system,  which  regulates 
the  organic  life.  This  consists  of  numerous  small  nerve  cen- 
ters arranged  in  oval  masses  varying  greatly  in  size,  called 
ganglia  or  knots.  These  are  either  scattered  irregularly  through 
the  body,  or  arranged  in  a  double  chain  of  knots  lying  on  the 
front  of  the  spine,  within  the  chest  and  abdomen.  From  this 
chain  large  numbers  of  nerves  are  given  off,  which  end  chiefly 
in  the  organs  of  digestion,  circulation,  and  respiration.  The 
sympathetic  system  serves  to  bring  all  portions  of  the  animal 
economy  into  direct  sympathy  with  one  another. 

266.  The  Brain  as  a  Whole.     The  brain  is  the  seat  of  the 
intellect,  the  will,  the  affections,  the  emotions,  the  memory,  and 
sensation.     It  has  also  many  other  and  complex  functions.     In 
it  are  established  many  reflex,  automatic,  and  coordinating  cen- 
ters, which  are  as  independent  of  consciousness  as  are  those 
of  the  spinal  cord. 


THE    NERVOUS    SYSTEM.  269 

The  brain  is  the  largest  and  most  complex  mass  of  nerve 
tissue  in  the  body,  made  up  of  an  enormous  collection  of  gray 
cells  and  nerve  fibers.  This  organ  consists  of  a  vast  number 
of  distinct  ganglia,  or  separate  masses  of  nerve  matter,  each 


FIG.  114.  —  The  Upper  Surface  of  the  Cerebrum.     (Showing  its  division 
into  two  hemispheres,  and  also  the  convolutions.) 

capable  of   performing  separate  functions,  but  united  through 
the  cerebral  action  into  a  harmonious  whole. 

The  average  weight  of  the  adult  human  brain  is  about  50 
ounces  for  men  and  45  ounces  for  women.  Other  things  being 
equal,  the  size  and  weight  of  the  brain  bear  a  general  relation 
to  the  mental  power  of  the  individual.  As  a  rule,  a  large, 
healthy  brain  stands  for  a  vigorous  and  superior  intellect. 
The  brains  of  many  eminent  men  have  been  found  to  be  8  to 
12  ounces  above  the  average  weight,  but  there  are  notable 


27O  PRACTICAL    PHYSIOLOGY. 

exceptions.  The  brains  of  idiots  are  small  ;  indeed,  any 
weight  under  a  certain  size,  about  30  ounces,  seems  to  be 
invariably  associated  with  an  imbecile  mind. 

The  human  brain  is  absolutely  heavier  than  that  of  any  other 
animal,  except  the  whale  and  elephant.  Comparing  the  size 
of  these  animals  with  that  of  man,  it  is  instructive  to  notice 
how  much  larger  in  proportion  to  the  body  is  man's  brain. 
The  average  proportion  of  the  weight  of  the  brain  to  the  weight 
of  the  body  is  greater  in  man  than  in  most  animals,  being 
about  i  to  36.  In  some  small  birds,  in  the  smaller  monkeys, 
and  in  some  rodents,  the  proportional  weight  of  the  brain  to 
that  of  the  body  is  even  greater  than  in  man. 

267.  The  Cerebrum.  The  three  principal  masses  which 
make  up  the  brain  when  viewed  as  a  whole  are  : 

1 .  The  cerebrum,  or  brain  proper. 

2.  The  cerebellum,  or  lesser  brain. 

3.  The  medulla  oblongata. 

The  cerebrum  comprises  nearly  seven-eighths  of  the  entire 
mass,  and  fills  the  upper  part  of  the  skull.  It  consists  of  two 
halves,  the  right  and  left  cerebral  hemispheres.  These  are 
almost  separated  from  each  other  by  a  deep  median  fissure. 
The  hemispheres  are  united  at  the  bottom  of  the  fissure  by  a 
mass  of  white  fibers  passing  from  side  to  side.  Each  of  these 
hemispheres  is  subdivided  into  three  lobes,  so  that  the  entire 
cerebrum  is  made  up  of  six  distinct  lobes. 

The  cerebrum  has  a  peculiar  convoluted  appearance,  its 
deep  folds  being  separated  by  fissures,  some  of  them  nearly  an 
inch  in  depth. 

It  is  composed  of  both  white  and  gray  matter.  The  former 
comprises  the  greater  part  of  the  mass,  while  the  .  latter  is 
spread  over  the  surface  in  a  layer  of  about  |  of  an  inch 
thick.  The  gray  matter  is  the  portion  having  the  highest 


THE    NERVOUS    SYSTEM.  27! 

functions,  and  its  apparent  quantity  is  largely  increased  by 
being  formed  in  convolutions. 

The  convolutions  of  the  cerebrum  are  without  doubt  associ- 
ated with  all  those  higher  actions  which  distinguish  man's  life; 
but  all  the  convolutions  are  not  of  equal  importance.  Thus  it 
is  probable  that  only  the  frontal  part  of  the  brain  is  the  intel- 
lectual region,  while  certain  convolutions  are  devoted  to  the 
service  of  the  senses. 

The  cerebrum  is  the  chief  seat  of  the  sensations,  the  intel- 
lect, the  will,  and  the  emotions.  A  study  of  cerebral  injuries 
and  diseases,  and  experiments  upon  the  lower  animals,  prove 
that  the  hemispheres,  and  more  especially  the  gray  matter,  are 
connected  with  mental  states.  The  convolutions  in  the  human 
brain  are  more  prominent  than  in  that  of  the  higher  animals, 
most  nearly  allied  to  man,  although  some  species  of  animals, 
not  especially  intelligent,  have  marked  cerebral  convolutions. 
The  higher  races  of  men  have  more  marked  convolutions  than 
those  less  civilized. 

A  view  of  the  under  surface  of  the  brain,  which  rests  on  the 
floor  of  the  skull,  shows  the  origin  of  important  nerves,  called 
the  cranial  nerves,  the  cerebellum,  the  structure  connecting 
the  Optic  nerves  (optic  commissure),  the  bridge  of  nervous 
matter  (pons  Varolii)  connecting  the  two  hemispheres  of  the 
cerebellum,  and  lastly  numerous  and  well-marked  convolutions. 

268.  The  Cerebellum.  The  cerebellum,  or  lesser  brain, 
lies  in  the  back  of  the  cranium,  and  is  covered  over  in  man  by 
the  posterior  lobe  of  the  cerebrum.  It  is,  at  it  were,  astride  of 
the  back  of  the  cerebro-spinal  axis,  and  consists  of  two  hemi- 
spheres joined  by  a  central  mass.  On  its  under  surface  is  a 
depression  which  receives  the  medulla  oblongata.  The  cere- 
bellum is  separated  from  the  cerebrum  by  a  horizontal  partition 
of  membrane,  a  portion  of  the  dura  mater.  In  some  animals, 
as  in  the  cat,  this  partition  is  partly  bone. 


2/2 


PRACTICAL    PHYSIOLOGY. 


The  cerebellum  is  connected  with  other  parts  of  the  nervous 
system  by  strands  of  white  matter  on  each  side,  radiating  from 
the  center  and  divided  into  numerous  branches.  Around  these 
branches  the  gray  matter  is  arranged  in  a  beautiful  manner, 
suggesting  the  leaves  of  a  tree  :  hence  its  name,  arbor  vitae, 
or  the  tree  of  life. 

The  functions  of  the  cerebellum  are  not  certainly  known. 
It  appears  to  influence  the  muscles  of  the  body  so  as  to  regu- 


FIG.  115.  — A  Vertical  Section  of  the  Brain. 

A,  frontal  lobe  of  the  cerebrum  ;  B,  parietal  lobe  ;  C,  parieto-occipital  lobe  with  fissure 
between  this  lobe  and  D,  the  occipital  lobe;  E,  cerebellum  ;  F,  arbor  vitae ;  H, 
pons  Varolii ;  K,  medulla  oblongata ;  L,  portion  of  lobe  on  the  opposite  side  of 
brain.  The  white  curved  band  above  H  represents  the  corpus  callosum. 

late  their  movements  ;  that  is,  it  serves  to  bring  the  various 
muscular  movements  into  harmonious  action.  The  mechanism 
by  which  it  does  this  has  not  yet  been  clearly  explained.  In 
an  animal  from  which  the  cerebellum  has  been  removed,  the 
functions  of  life  do  not  appear  to  be  destroyed,  but  all  power 
of  either  walking  or  flying  straight  is  lost. 


THE    NERVOUS    SYSTEM.  2/3 

Disease  or  injury  of  the  cerebellum  usually  produces  blind- 
ness, giddiness,  a  tendency  to  move  backwards,  a  staggering, 
irregular  gait,  and  a  feeling  of  insecurity  in  maintaining  various 
positions.  There  is  no  loss  of  consciousness,  or  other  disturb- 
ance of  the  mental  functions. 

269.  The  Membranes  of  the  Brain.     The  brain  and  spinal 
cord  are  protected  by  three  important  membranes,  known  as 
the  meninges, — the  dura  mater,  the  arachnoid,  and  the  pia 
mater. 

The  outer  membrane,  the  dura  mater,  is  much  thicker  and 
stronger  than  the  others,  and  is  composed  of  white  fibrous  and 
elastic  connective  tissue.  It  closely  lines  the  inner  surface  of 
the  skull,  and  forms  a  protective  covering  for  the  brain.  Folds 
of  it  pass  between  the  several  divisions  of  the  brain  and  serve 
to  protect  them. 

The  arachnoid  is  a  thin  membrane  which  lies  beneath  the 
dura  mater.  It  secretes  a  serous  fluid  which  keeps  the  inner 
surfaces  moist. 

The  pia  mater  is  a  very  delicate,  vascular  membrane  which 
covers  the  convolutions,  dips  into  all  the  fissures,  and  even 
penetrates  into  the  interior  of  the  brain.  It  is  crowded  with 
blood-vessels,  which  divide  and  subdivide  very  minutely  before 
they  penetrate  the  brain.  The  membranes  of  the  brain  are 
sometimes  the  seat  of  inflammation,  a  serious  and  painful  dis- 
ease, commonly  known  as  brain  fever. 

270.  The  Medulla  Oblongata.     This  is  the  thick  upper  part 
of  the  spinal  cord,  lying  within  the  cavity  of  the  skull.     It  is 
immediately  under  the  cerebellum,  and  forms  the  connecting 
link  between  the  brain  and  the  spinal  cord.     It  is  about  an 
inch  and  a  quarter  long,  and  from  one-half  to  three-fourths  of 
an  inch  wide  at  its  upper  part.     The  medulla  oblongata  con- 
sists,   like   the   spinal   cord,  of    columns   of    white   fibers   and 


2/4  PRACTICAL    PHYSIOLOGY. 

masses  of  gray  matter,  but  differently  arranged.  The  gray 
matter  is  broken  up  into  masses  which  serve  as  centers  of 

origin  for  various  nerves. 

The  functions  of  the  me- 
dulla oblongata  are  closely 
connected  with  the  vital  proc- 
esses. It  is  a  great  nerve 
tract  for  transmitting  sensory 
and  motor  impressions,  and 
also  the  seat  of  a  number 
of  centers  for  reflex  actions 
of  the  highest  importance  to 
life.  Through  the  posterior 
part  of  the  medulla  the  sen- 
sory impressions  pass,  that 
is,  impressions  from  below 
upwards  to  the  brain  result- 
ing in  sensation  or  feeling. 
In  the  anterior  part  of  the 
medulla,  pass  the  nerves  for 
motor  transmission,  that  is, 
nerve  influences  from  above 
downwards  that  shall  result 
in  muscular  contractions  in 
some  part  of  the  body. 

FIG.  1 16.— Illustrating  the  General  Arrange-         The     medulla    is    also    the 
ment  of  the  Nervous  System.     (Posterior    seat    of    a    number    of    reflex 

centers  connected   with  the 

influence  of  the  nervous  system  on  the  blood-vessels,  the  move- 
ments of  the  heart,  of  respiration,  and  of  swallowing,  and  on  the 
secretion  of  saliva.  This  spot  has  been  called  the  "vital  knot." 
In  the  medulla  also  are  centers  for  coughing,  vomiting,  swal- 
lowing, and  the  dilatation  of  the  pupil  of  the  eye.  It  is  also  in 
part  the  deep  origin  of  many  of  the  important  cranial  nerves. 


THE    NERVOUS    SYSTEM.  2/5 

271.   The  Cranial  Nerves.     The  cranial  or  cerebral  nerves 

consist  of  twelve  pairs  of  nerves  which  pass  from  the  brain 
through  different  openings  in  the  base  of  the  skull,  and  are 
distributed  over  the  head  and  face,  also  to  some  parts  of  the 
trunk  and  certain  internal  organs.  These  nerves  proceed  in 
pairs  from  the  corresponding  parts  of  each  side  of  the  brain, 
chiefly  to  the  organs  of  smell,  taste,  hearing,  and  sight. 

The  cranial  nerves  are  of  three  kinds  :  sensory,  motor,  and 
both  combined,  viz.,  mixed. 

Distribution  and  Functions  of  the  Cranial  Nerves.  The  cranial 
nerves  are  thus  arranged  in  pairs  : 

The  first  pair  are  the  olfactory  nerves,  which  pass  down  through 
the  ethmoid  bone  into  the  nasal  cavities,  and  are  spread  over  the  inner 
surface  of  the  nose.  They  are  sensory,  and  are  the  special  nerves 
of  smell. 

The  second  pair  are  the  optic  nerves,  which,  under  the  name  of 
the  optic  tracts,  run  down  to  the  base  of  the  brain,  from  which  an 
optic  nerve  passes  to  each  eyeball.  These  are  sensory  nerves,  and 
are  devoted  to  sight. 

The  third,  fourth,  and  sixth  pairs  proceed  to  the  muscles  of  the 
eyes  and  control  their  movements.  These  are  motor  nerves,  the 
movers  of  the  eye. 

Each  of  the  fifth  pair  of  nerves  is  in  three  branches,  and  proceeds 
mainly  to  the  face.  They  are  called  tri-facial,  and  are  mixed  nerves, 
partly  sensory  and  partly  motor.  The  first  branch  is  purely  sensory, 
and  gives  sensibility  to  the  eyeball.  The  second  gives  sensibility  to 
the  nose,  gums,  and  cheeks.  The  third  (mixed)  gives  the  special 
sensation  of  taste  on  the  front  part  of  the  tongue,  and  ordinary  sen- 
sation on  the  inner  side  of  the  cheek,  on  the  teeth,  and  also  on  the 
scalp  in  front  of  the  ear.  The  motor  branches  supply  the  chewing 
muscles. 

The  seventh  pair,  the  facial,  proceed  to  the  face,  where  they 
spread  over  the  facial  muscles  and  control  their  movements.  The 
eighth  pair  are  the  auditory,  or  nerves  of  hearing,  and  are  distributed 
to  the  special  organs  of  hearing. 


PRACTICAL    PHYSIOLOGY. 


The  next  three  pairs  of  nerves  all  arise  from  the  medulla,  and 
escape  from  the  cavity  of  the  skull  through  the  same  foramen.  They 
are  sometimes  described  as  one  pair,  namely,  the  eighth,  but  it  is 
more  convenient  to  consider  them  separately. 

The  ninth  pair,  the  glosso-pharyngeal,  are  partly  sensory  and  partly 
motor.  Each  nerve  contains  two  roots  : 
one  a  nerve  of  taste,  which  spreads  over 
the  back  part  of  the  tongue  ;  the  other  a 
motor  nerve,  which  controls  the  muscles 
engaged  in  swallowing. 

The  tenth  pair,  the  pneumogastric,  also 
known  as  the  vagus  or  wandering  nerves, 
are  the  longest  and  most  complex  of  all  the 
cranial  nerves.  They  are  both  motor  and 
sensory,  and  are  some  of  the  most  impor- 
tant nerves  in  the  body.  Passing  from  the 
medulla  they  descend  near  the  oesophagus 
to  the  stomach,  sending  off,  on  their  way, 
branches  to  the  throat,  the  larynx,  the  lungs, 
and  the  heart.  Some  of  their  branches 
restrain  the  movements  of  the  heart,  others 
convey  impressions  to  the  brain,  which 
result  in  quickening  or  slowing  the  move- 
ments  of  breathing.  Other  branches  pass 
to  the  stomach,  and  convey  to  the  brain 
-Passions  which  inform  us  of  the  con- 
munis;  D,  fifth  nerve;  E,  motor  dition  of  that  organ.  These  are  the  nerves 

E—  s^Wszi  ^.  which  we  experience  the  feelings  o£ 

pharyngeal  nerve;  K,  pneumo-  pain  in  the  stomach,  hunger,  nausea,  and 
r±^'±v^;a™;  ™»X  other  vague  impressions  which  we 
extremity  of  spinal  cord;  o,  often  associate  with  that  organ. 

decussation  of  the  anterior  pyra-  —,,         ,  ,  ,          .        ,  .       , 

mids  ;  R,  anterior  pyramids  of  The  eleventh  pair,  the  spinal  accessory. 
the  medulla  oblongata  ;  s,  pons  are  strictly  motor,  and  supply  the  muscles 

of  the  neck  and  the  back. 

The  twelfth  pair,  the  hypoglossal,  are  also  motor,  pass  to  the 
muscles  of  the  tongue,  and  help  control  the  delicate  movements  in 
the  act  of  speech. 


FIG.  117.  —  Anterior  View  of 
the  Medulla  Oblongata. 


THE    NERVOUS    SYSTEM. 

272.  The  Spinal  Cord.     This  is  a  long,  rod-like  mass  of 
white  nerve  fibers,  surrounding  a  central  mass  of  gray  matter. 
It  is  a  continuation  of  the  medulla  oblongata,  and  is  lodged 
in  the  canal  of  the  spinal  column.     It  extends  from  the  base 
of  the  skull  to  the  lower  border  of  the  first  lumbar  vertebra, 
where  it  narrows  off  to  a  slender  filament  of  gray  substance. 

The  spinal  cord  is  from  16  to  18  inches  long,  and  has  about 
che  thickness  of  one's  little  finger,  weighing  about  i^  ounces. 
Like  the  brain,  it  is  enclosed  in  three  membranes,  which  in 
fact  are  the  continuation  of  those  within  the  skull.  They 
protect  the  delicate  cord,  and  convey  vessels  for  its  nourish- 
ment. The  space  between  the  two  inner  membranes  contains 
a  small  quantity  of  fluid,  supporting  the  cord,  as  it  were  in  a 
water-bath.  It  is  thus  guarded  against  shocks. 

The  cord  is  suspended  and  kept  in  position  in  the  canal  by 
delicate  ligaments  at  regular  intervals  between  the  inner  and 
outer  membranes.  Finally,  between  the  canal,  enclosed  by  its 
three  membranes,  and  the  bony  walls  of  the  spinal  canal, 
there  is  considerable  fatty  tissue,  a  sort  of  packing  material, 
imbedded  in  which  are  some  large  blood-vessels. 

273.  Structure  of  the  Spinal  Cord.     The  arrangement  of 
the  parts  of  the  spinal  cord  is  best  understood  by  a  transverse 
section.     Two  fissures,,  one  behind,  the  other  in  front,  pene- 
trate deeply  into  the  cord,  very  nearly  dividing  it  into  lateral 
halves.      In  the  middle  of   the  isthmus  which  joins  the  two 
halves,  is  a  very  minute  opening,  the  central  canal  of  the  cord. 
This  tiny  channel,  just  visible  to  the  naked  eye,  is  connected 
with  one  of  the  openings  of  the  medulla  oblongata,  and  extends, 
as  do  the  anterior  and  posterior  fissures,  the  entire  length  of 
the  cord. 

The  spinal  cord,  like  the  brain,  consists  of  gray  and  white 
matter,  but  the  arrangement  differs.  In  the  brain  the  white 
matter  is  within,  and  the  gray  matter  is  on  the  surface.  In 


278  PRACTICAL    PHYSIOLOGY. 

the  cord  the  gray  matter  is  arranged  in  two  half-moon-shaped 
masses,  the  backs '  of  which  are  connected  at  the  central  part. 
The  white  matter,  consisting  mainly  of  fibers,  running  for  the 
most  part  in  the  direction  of  the  length  of  the  cord,  is  outside 
of  and  surrounds  the  gray  crescents.  Thus  each  half  or  side 
of  the  cord  has  its  own  gray  crescent,  the  horns  of  which  point 
one  forwards  and  the  other  backwards,  called  respectively  the 
anterior  and  posterior  cornua  or  horns. 

It  will  also  be  seen  that  the  white  substance  itself,  in  each 
half  of  the  cord,  is  divided  by  the  horns  of  the  gray  matter 
and  by  fibers  passing  from  them  into  three  parts,  which  are 
known  as  the  anterior,  posterior,  and  lateral  columns. 

Experiment  130.  Procure  at  the  market  an  uninjured  piece  of  the  spinal 
cord  from  the  loin  of  mutton  or  the  sirloin  or  the  rib  of  beef.  After  noting 
its  general  character  while  fresh,  put  it  to  soak  in  dilute  alcohol,  until  it  is 
sufficiently  hard  to  be  cut  in  sections. 

274.  The  Spinal  Nerves.  From  the  gray  matter  on  each 
side  of  the  spinal  cord  31  spinal  nerves  are  given  off  and  dis- 
tributed chiefly  to  the  muscles  and  the  skin.  They  pass  out 
at  regular  intervals  on  each  side  of  the  canal,  by  small  open- 
ings between  the  vertebrae.  Having  escaped  from  the  spine, 
they  pass  backwards  and  forwards,  ramifying  in  the  soft  parts 
of  the  body.  The  first  pair  pass  out  between  the  skull  and 
the  atlas,  the  next  between  the  atlas  and  the  axis,  and  so  on 
down  the  canal.  The  eighth  pair,  called  cervical,  pass  out  in 
the  region  of  the  neck  ;  twelve,  called  dorsal,  in  the  region  of 
the  ribs  ;  five  are  lumbar,  and  five  sacral,  while  the  last  pair 
leave  the  cord  near  the  coccyx. 

Each  spinal  nerve  has  two  roots,  one  from  the  anterior,  the 
other  from  the  posterior  portion  of  the  cord.  These  unite  and 
run  side  by  side,  forming  as  they  pass  between  the  vertebra 
one  silvery  thread,  or  nerve  trunk.  Although  bound  up  in  one 
bundle,  the  nerve  fibers  of  the  two  roots  remain  quite  distinct, 
and  perform  two  entirely  different  functions. 


THE    NERVOUS    SYSTEM. 


279 


C-r 


After  leaving  the  spinal  cord,  each  nerve  divides  again  and 
again  into  finer  and  finer  threads.  These  minute  branches  are 
distributed  through  the  muscles,  and  terminate  on  the  surface 
of  the  body.  The  anterior  roots  become  motor  nerves,  their 
branches  being  distributed  to  cer- 
tain muscles  of  the  body,  to  control 
their  movements.  The  posterior  roots 
develop  into  sensory  nerves,  their 
branches  being  distributed  through 
the  skin  and  over  the  surface  of  the 
body  to  become  nerves  of  touch.  In 
brief,  the  spinal  nerves  divide  and 
subdivide,  to  reach  with  their  twigs 
all  parts  of  the  body,  and  provide 
every  tissue  with  a  nerve  center,  a 
station  from  which  messages  may  be 
sent  to  the  brain. 

A,  anterior  median  fissure ;   B,  pos- 

275.  The  Functions  Of  the  Spinal        tenor  median  fissure;  C,  anterior 

Nerves.     The  messages  which  pass 

along  the  spinal  nerves  to  and  from 

the    brain    are    transmitted     mostly 

through  the  gray  matter  of  the  cord, 

but  some  pass  along  the  white  matter 

on  the  outer  part.     As  in  the  brain,  however,  all  the  active 

powers  of  the  cord  are  confined  to  the  gray  matter.      The 

spinal  nerves  themselves  have  nothing  to  do  with  sensation  or 

will.     They  are  merely  conductors  to  carry  messages  to  and 

fro.      They    neither    issue    commands    nor   feel    a    sensation. 

Hence,  they  consist  entirely  of  white  matter. 

276.  Functions  of  the  Spinal  Cord.     The  spinal  cord  is 
the   principal   channel  through   which   all    impulses  from  the 
trunk  and  extremities  pass  to  the  brain,  and  all  impulses  to 
the  trunk  and  extremities  pass  from  the  brain.     That  is,  the 


FIG.  118.  — Side  View  of  the 
Spinal  Cord.  (Showing  the 
fissures  and  columns.) 


lateral  fissure  ;  D,  posterior  lateral 
fissure  ;  E,  lateral  column  ;  F,  an- 
terior column;  G,  posterior  col- 
umn ;  H,  posterior  median  col- 
umn; K,  anterior  root ;  L,  posterior 
root;  M,  ganglion  of  N,  a  spinal 
nerve. 


28O  PRACTICAL  PHYSIOLOGY. 

spinal  cord  receives  from  various  parts  of  the  body  by  means 
of  its  sensory  nerves  certain  impressions,  and  conveys  them 
to  the  brain,  where  they  are  interpreted. 

The  cord  also  transmits  by  means  of  its  motor  nerves  the 
commands  of  the  brain  to  the  voluntary  muscles,  and  so  causes 
movement.  Thus,  when  the  cord  is  divided  at  any  point,  com- 
pressed, as  by  a  tumor  or  broken  bone,  or  disorganized  by  dis- 
ease, the  result  is  a  complete  loss  of  sensation  and  voluntary 
movement  below  the  point  of  injury.  If  by  accident  a  man 
has  his  spinal  cord  injured  at  some  point,  he  finds  he  has  lost 
all  sensation  and  power  of  motion  below  that  spot.  The  im- 
pulse to  movement  started  in  his  brain  by  the  will  does  not 
reach  the  muscles  he  wishes  to  move,  because  traveling  down 
the  spinal  cord,  it  cannot  pass  the  seat  of  injury. 

So  the  impression  produced  by  pricking  the  leg  with  a  pin, 
which,  before  pain  can  be  felt,  must  travel  up  the  spinal  cord 
to  the  brain,  cannot  reach  the  brain  because  the  injury  obstructs 
the  path.  The  telegraph  wire  has  been  cut,  and  the  current 
can  no  longer  pass. 

277.   The  Spinal  Cord  as  a  Conductor  of  Impulses.     The 

identity  in  structure  of  the  spinal  nerves,  whether  motor  or 
sensory,  and  the  vast  number  of  nerves  in  the  cord  make  it 
impossible  to  trace  for  any  distance  with  the  eye,  even  aided 
by  the  microscope  and  the  most  skillful  dissection,  the  course 
of  nerve  fibers.  The  paths  by  which  the  motor  impulses  travel 
down  the  cord  are  fairly  well  known.  These  impulses  origi- 
nate in  the  brain,  and  passing  down  keep  to  the  same  side 
of  the  cord,  and  go  out  by  nerves  to  the  same  side  of  the 
body. 

The  sensory  impulses,  however,  soon  after  they  enter  the 
cord  by  the  nerve  of  one  side,  cross  in  the  cord  to  the  opposite 
side,  up  which  they  travel  to  the  brain.  Thus  the  destruction 
of  one  lateral  half  of  the  cord  causes  paralysis  of  motion  on 


THE    NERVOUS    SYSTEM. 


281 


the  same  side  as  the  injury,  but  loss  of  sensation  on  the  oppo- 
site side,  because  the  posterior  portion  destroyed  consists  of 
fibers  which  have  crossed  from  the  opposite  side. 

Experiment  proves  that  if  both  roots  of  a  spinal  nerve  be 
cut,  all  those  parts 
of  the  body  to 
which  they  send 
branches  become 
paralyzed,  and 
ha ve  neither 
sense  of  pain  nor 
power  of  volun- 
tary movement. 
The  parts  might 
even  be  cut  or 
burned  without 
pain.  It  is  pre- 
cisely like  cutting 
a  telegraph  wire 
and  stopping  the 
current. 

Experi  men  t 
also   proves    that 

FIG.  119. —  The  Base  of  the  Brain. 

A,  anterior  lobe  of  the  cerebrum  ;  B,  olfactory  nerve ;  C,  sphen- 
oid portion  of  the  posterior  lobe ;  D,  optic  chiasm ;  E,  optic 
tract;  F,  abducens;  H,  M,  hemispheres  of  the  cerebellum; 
K,  occipital  portion  of  the  occipital  lobe ;  L,  fissure  separat- 
ing the  hemispheres ;  N,  medulla  oblongata ;  O,  olivary  body  ; 
P,  anterior  pyramids;  R,  pons  Valorii ;  S,  section  of  olfactory 


if  only  the  pos- 
terior root  of  a 
spinal  nerve  be 
cut,  all  sensation 
is  lost  in  the  parts 
to  which  the  nerve 
passes,  but  the 
power  of  moving  these  parts  is  retained.  But  if  the  anterior 
root  alone  be  divided,  all  power  of  motion  in  the  parts  supplied 
by  that  nerve  is  lost,  but  sensation  remains.  From  these  and 
many  other  experiments,  it  is  evident  that  those  fibers  of  a 


nerve,  with  the  trunk  removed  to  show  sulcus  in  which  it  is 
lodged ;  T,  anterior  extremity  of  median  fissure. 


282  PRACTICAL    PHYSIOLOGY. 

nerve  which  are  derived  from  the  anterior  root  are  motor,  and 
those  from  the  posterior  root  sensory,  fibers.  Impulses  sent 
from  the  brain  and  spinal  cord  to  muscles  will,  therefore,  pass 
along  the  anterior  roots  through  those  fibers  of  the  nerves 
which  are  derived  from  these  (motor)  roots.  On  the  other 
hand,  impressions  or  sensations  passing  to  the  brain  will  enter 
the  spinal  cord  and  reach  the  brain  through  the  posterior  or 
sensory  roots. 

278.  The  Spinal  Cord  as  a  Reflex  Center.     Besides  this 
function  of  the  spinal  cord  as  a  great  nerve  conductor  to  carry 
sensations  to  the  brain,  and  bring  back  its  orders,  it  is  also  an 
independent  center  for  what  is  called  reflex  action.     By  means 
of  its  sensory  nerves  it  receives  impressions  from  certain  parts 
of  the  body,  and  on  its  own  authority  sends  back  instructions 
to  the  muscles  by  its  motor  nerves,  without  consulting   the 
brain.     This  constitutes  reflex  action,  so  called  because  the 
impulse  sent  to  the  spinal  cord  by  certain  sensory  nerves  is 
at  once  reflected  or    sent  back  as  a  motor   impulse  to  the 
muscles. 

This  reflex  action  is  a  most  important  function  of  the  spinal 
cord.  This  power  is  possessed  only  by  the  gray  matter  of  the 
cord,  the  white  substance  being  simply  a  conductor. 

The  cells  of  gray  matter  are  found  all  along  the  cord,  but 
are  grouped  together  in  certain  parts,  notably  in  the  cervical 
and  lumbar  regions.  The  cells  of  the  anterior  horns  are  in 
relation  with  the  muscles  by  means  of  nerve  fibers,  and  are 
also  brought  into  connection  with  the  skin  and  other  sensory 
surfaces,  by  means  of  nerve  fibers  running  in  the  posterior 
part  of  the  cord.  Thus  there  is  established  in  the  spinal  cord, 
without  reference  to  the  brain  at  all,  a  reflex  mechanism. 

279.  Reflex  Centers.     For  the  purpose  of  illustration,  we 
might  consider  the  body  as  made  up  of  so  many  segments  piled 


THE    NERVOUS    SYSTEM.  283 

one  on  another,  each  segment  presided  over  by  a  similar  seg- 
ment of  spinal  cord.  Each  bodily  segment  would  have  sensory 
and  motor  nerves  corresponding  to  its  connection  with  the 
spinal  cord.  The  group  of  cells  in  each  spinal  segment  is 
intimately  connected  with  the  cells  of  the  segments  above  and 
below.  Thus  an  impression  reaching  the  cells  of  one  spinal 
segment  might  be  so  strong  as  to  overflow  into  the  cells  of 
other  segments,  and  thus  cause  other  parts  of  the  body  to  be 
affected. 

Take  as  an  example  the  case  of  a  child  who  has  eaten  im- 
proper food,  which  irritates  its  bowels.  Sensory  nerves  of  the 
bowels  are  disturbed,  and  powerful  impressions  are  carried  up 
to  a  center  in  the  spinal  cord.  These  impressions  may  now 
overflow  into  other  centers,  from  which  spasmodic  discharges 
of  nerve  energy  may  be  liberated,  which  passing  to  the  muscles, 
throw  them  into  violent  and  spasmodic  contraction.  In  other 
words,  the  child  has  a  fit,  or  convulsion.  All  this  disturbance 
being  the  result  of  reflex  action  (the  spasmodic  motions  being 
quite  involuntary,  as  the  brain  takes  no  part  in  them),  the  child 
meanwhile  is,  of  course,  entirely  unconscious  and,  however  it 
may  seem  to  be  distressed,  really  suffers  no  pain. 

Scattered  along  the  entire  length  of  the  spinal  cord,  espe- 
cially in  the  upper  part,  are  groups  of  nerve  cells  which  preside 
over  certain  specific  functions  of  animal  life  ;  that  is,  definite 
collections  of  cells  which  control  definite  functions.  Thus 
there  are  certain  centers  for  maintaining  the  action  of  the 
heart,  and  the  movements  of  breathing;  and  low  down  in  the 
cord,  in  the  lumbar  regions,  are  centers  for  the  control  of 
the  various  abdominal  organs. 

Numerous  other  reflex  centers  are  described  by  physiologists, 
but  enough  has  been  said  to  emphasize  the  great  importance 
of  the  spinal  cord  as  an  independent  nerve  center,  besides  its 
function  as  a  conductor  of  nervous  impulses  to  and  from  the 
brain. 


284  PRACTICAL  PHYSIOLOGY. 

280.  The  Brain  as  a  Reflex  Center.     The  brain,  as  we 
have  just  stated,  is  the  seat  of  consciousness  and  intelligence. 
It  is  also  the  seat  of  many  reflex,  automatic,  and  coordinating 
centers.     These  give  rise  to  certain  reflex  actions  which  are 
as   entirely   independent    of    consciousness    as    are   those   of 
the  spinal  cord.     These  acts  take  place  independently  of  the 
will,  and   often   without  the   consciousness   of  the  individual. 
Thus,  a  sudden  flash  of  light  causes  the  eyes  to  blink,  as  the 
result  of  reflex  action.     The  optic  nerves  serve  as  the  sensory, 
and  the  facial  nerves  as  the  motor,  conductors.     The  sudden 
start  of   the  whole  body  at  some  loud  noise,  the  instinctive 
dodging  a  threatened  blow,  and  the  springing  back  from  sud- 
den danger,  are  the  results  of  reflex  action.     The  result  ensues 
in  these  and  in  many  other  instances,  without  the  conscious- 
ness of  the  individual,  and  indeed  beyond  his  power  of  control. 

281.  The  Importance  of  Reflex  Action.     Reflex  action  is 
thus  a  marvelous  provision  of  nature  for  our  comfort,  health, 
and  safety.     Its  vast  influence  is  not  realized,  as  its  number- 
less acts  are  so  continually  going  on  without  our  knowledge. 
In  fact,  the  greater  part  of  nerve  power  is  expended  to  produce 
reflex  action.     The  brain  is  thus  relieved  of  a  vast  amount  of 
work.     It  would  be  impossible  for  the  brain  to  serve  as   a 
"  thinking  center  "  to  control  every  act  of  our  daily  life.     If 
we  had  to  plan  and  to  will  every  heart-beat  or  every  respira- 
tion, the  struggle  for  life  would  soon  be  given  up. 

The  fact  that  the  gray  cells  of  the  spinal  cord  can  originate 
a  countless  number  of  reflex  and  automatic  activities  is  not 
only  of  great  importance  in  protecting  the  body  from  injury, 
but  increases  vastly  the  range  of  the  activities  of  our  daily  life. 

Even  walking,  riding  the  bicycle,  playing  on  a  piano,  and 
numberless  other  such  acts  may  be  reflex  movements.  To 
learn  how,  requires,  of  course,  the  action  of  the  brain,  but  by 
frequent  repetition  the  muscles  become  so  accustomed  to  cer- 


THE    NERVOUS    SYSTEM. 


285 


tain  successive  movements,  that  they  are  continued  by  the  cord 
without  the  control  of  the  brain.  Thus  we  may  acquire  a  sort 
of  artificial  reflex  action,  which  in  time  becomes  in  a  way  a 
part  of  our  organization,  and  is  carried  on  without  will  power 
or  even  consciousness. 

So,  while  the  hands  are  busily  doing 
one  thing,  the  brain  can  be  intently 
thinking  of  another.  In  fact,  any  at- 
tempt to  control  reflex  action  is  more 
apt  to  hinder  than  to  help.  In  coming 
rapidly  down  stairs,  the  descent  will  be 
made  with  ease  and  safety  if  the  spinal 
cord  is  allowed  entire  charge  of  the  FIG.  120. -Dr.  Waller's  Dia- 
act,  but  the  chances  of  Stumbling  or  grammatic  Illustration  of  the 

f  ,      .  ,        Reflex  Process, 

of   tripping   are   very   much  increased 

From  the  sentient  surface  (1)  an 

if  each  step  be  taken  as  the  result  of  afferent  impulse  passes  along 
the  will  power.  The  reflex  action  of  <2)  to  the  posterior  root  of  the 

spinal  cord,  the  nerve  fibers  of 

the  cord  may  be  diminished,  or  in-  the  posterior  root  ending  in 
hibited  as  it  is  called,  but  this  power  minute  "laments  among  the 

. .      .       ,  small  cells  of  this  part  of  the 

is  limited.  Thus,  we  can  by  an  effort  cord  (3).  In  some  unknown 
of  the  will  stop  breathing  for  a  certain  wa? this  impulse  passes  across 

the  gray  part  of  the  cord  to  the 

time,  but  beyond  that  the  renex  mech- 


large  cells  of  the  anterior  root 
(5),  the  cells  of  this  part  being 
connected  by  their  axis-cylinder 
with  the  efferent  fibers  (6). 
These  convey  the  stimulus  to 
the  fibers  of  the  muscle  (7), 
which  accordingly  contract. 
Where  the  brain  is  concerned 
in  the  action  the  circuit  is  longer 
through  S  and  M. 

Experiment  131.  To  illustrate  reflex  action  by  what  is  called  knee-jerk. 
Sit  on  a  chair,  and  cross  the  right  leg  over  the  left  one.  With  the  tips  of 
the  ringers  or  the  back  of  a  book,  strike  the  right  ligamentum  patellae. 
The  right  leg  will  be  raised  and  thrown  forward  with  a  jerk,  owing  to  the 
contraction  of  the  quadriceps  muscles.  An  appreciable  time  elapses  be- 
tween the  striking  of  the  tendon  and  the  jerk.  The  presence  or  absence 
of  the  knee-jerk  may  be  a  most  significant  symptom  to  the  physician. 


anism  overcomes  our  will  and  we  could 
not,  if  we  would,  commit  suicide  by 
holding  our  breath.  When  we  are 
asleep,  if  the  palm  of  the  hand  be 
tickled,  it  closes  ;  when  we  are  awake 
we  can  prevent  it. 


286  PRACTICAL  PHYSIOLOGY. 

282.  The  Sympathetic  System.     Running  along  each  side 
of  the  spine,  from  the  base  of  the  skull  to  the  coccyx,  is  a 
chain  of  nerve  knots,  or  ganglia.     These  ganglia,  twenty-four 
on  each  side,  and  their  branches  form  the  sympathetic  system, 
as  distinguished  from  the  cerebro-spinal  system  consisting  of 
the  brain  and  spinal  cord  and  the  nerves  springing  from  them. 
The  ganglia  of  the  sympathetic  system  are  connected  with  each 
other  and  with  the  sensory  roots  of  the  spinal  nerves  by  a  net- 
work of  gray  nerve  fibers. 

At  the  upper  end  the  chain  of  each  side  passes  up  into  the 
cranium  and  is  closely  connected  with  the  cranial  nerves.  In 
the  neck,  branches  pass  to  the  lungs  and  the  heart.  From  the 
ganglia  in  the  chest  three  nerves  form  a  complicated  network 
of  fibers,  from  which  branches  pass  to  the  stomach,  the  liver, 
the  intestines,  the  kidneys,  and  other  abdominal  organs.  A 
similar  network  of  fibers  is  situated  lower  down  in  the  pelvis, 
from  which  branches  are  distributed  to  the  pelvic  organs.  At 
the  coccyx  the  two  chains  unite  into  a  single  ganglion. 

Thus,  in  general,  the  sympathetic  system,  while  intimately 
connected  with  the  cerebro-spinal,  forms  a  close  network  of 
nerves  which  specially  accompany  the  minute  blood-vessels, 
and  are  distributed  to  the  muscles  of  the  heart,  the  lungs,  the 
stomach,  the  liver,  the  intestines,  and  the  kidneys  —  that  is, 
the  hollow  organs  of  the  body. 

283.  The  Functions  of  the  Sympathetic  System.     This 
system  exercises  a  superintending  influence  over  the  greater 
part  of  the  internal  organs  of  the  body,  controlling  to  a  certain 
extent  the  functions  of  digestion,  nutrition,  circulation,  and 
respiration.     The  influence  thus  especially  connected  with  the 
processes  of  organic  life  is  generally  different  from,  or  even 
opposed  to,  that  conveyed  to  the  same  organs  by  fibers  running 
in  the  spinal  or  cranial  nerves.     These  impulses  are  beyond 
the  control  of  the  will. 


THE    NERVOUS    SYSTEM. 


287 


FIG.  121.  —  The  Cervical  and  Thoracic  Portion  of  the  Sympathetic  Nerve 
and  its  Main  Branches. 

A,  right  pneumogastric ;  B,  spinal  accessory ;  C,  glosso-pharyngeal ;  D,  right  bronchus  ; 
E,  right  branch  of  pulmonary  artery;  F,  one  of  the  intercostal  nerves;  H,  great 
splanchnic  nerve  ;  K,  solar  plexus ;  L,  left  pneumogastric  ;  M,  stomach  branches  of 
right  pneumogastric;  N,  right  ventricle;  O,  right  auricle;  P,  trunk  of  pulmonary 
artery;  R,  aorta;  S,  cardiac  nerves;  T,  recurrent  laryngeal  nerve;  U,  superior 
laryngeal  nerve  ;  V,  submaxillary  ganglion ;  W,  lingual  branch  of  the  sth  nerve ; 
X,  ophthalmic  ganglion ;  Y,  motor  oculi  externus. 


288  PRACTICAL  PHYSIOLOGY. 

Hence,  all  these  actions  of  the  internal  organs  just  mentioned 
that  are  necessary  to  the  maintenance  of  the  animal  life,  and  of 
the  harmony  which  must  exist  between  them,  are  controlled  by 
the  sympathetic  system.  But  for  this  control,  the  heart  would 
stop  beating  during  sleep,  digestion  would  cease,  and  breathing 
would  be  suspended.  Gentle  irritation  of  these  nerves,  in- 
duced by  contact  of  food  in  the  stomach,  causes  that  organ 
to  begin  the  churning  motion  needed  for  digestion.  Various 
mental  emotions  also  have  a  reflex  action  upon  the  sympathetic 
system.  Thus,  terror  dilates  the  pupils,  fear  acts  upon  the 
nerves  of  the  small  blood-vessels  of  the  face  to  produce  pallor, 
and  the  sight  of  an  accident,  or  even  the  emotions  produced  by 
hearing  of  one,  may  excite  nausea  and  vomiting. 

The  control  of  the  blood- vessels,  as  has  been  stated  (sec. 
195),  is  one  of  the  special  functions  of  the  sympathetic  system. 
Through  the  nerves  distributed  to  the  muscular  coats  of  the 
arteries,  the  caliber  of  these  vessels  can  be  varied,  so  that  at 
one  moment  they  permit  a  large  quantity  of  blood  to  pass,  and 
at  another  will  contract  so  as  to  diminish  the  supply.  This, 
too,  is  beyond  the  control  of  the  will,  and  is  brought  about  by 
the  vaso-motor  nerves  of  the  sympathetic  system  through  a  re- 
flex arrangement,  the  center  for  which  is  the  medulla  oblongata. 

284.  Need  of  Rest.  The  life  of  the  body,  as  has  been  em- 
phasized in  the  preceding  chapters,  is  subject  to  constant  waste 
going  on  every  moment,  from  the  first  breath  of  infancy  to  the 
last  hour  of  old  age.  We  should  speedily  exhaust  our  life  from 
this  continual  loss,  but  for  its  constant  renewal  with  fresh 
material.  This  exhaustion  of  life  is  increased  by  exertion, 
and  the  process  of  repair  is  vastly  promoted  by  rest.  Thus, 
while  exercise  is  a  duty,  rest  is  equally  imperative. 

The  eye,  when  exactingly  used  in  fine  work,  should  have 
frequent  intervals  of  rest  in  a  few  moments  of  darkness  by 
closing  the  lids.  The  brain,  when  urged  by  strenuous  study, 


THE  NERVOUS  SYSTEM.  289 

should  have  occasional  seasons  of  rest  by  a  dash  of  cold  water 
upon  the  forehead,  and  a  brief  walk  with  slow  and  deep  inspi- 
rations of  fresh  air.  The  muscles,  long  cramped  in  a  painful 
attitude,  should  be  rested  as  often  as  may  be,  by  change  of 
posture  or  by  a  few  steps  around  the  room. 

It  is  not  entirely  the  amount  of  work  done,  but  the  continuity 
of  strain  that  wears  upon  the  body.  Even  a  brief  rest  inter- 
rupts this  strain  ;  it  unclogs  the  wheels  of  action.  Our  bodies 
are  not  designed  for  continuous  toil.  An  alternation  of  labor 
and  rest  diminishes  the  waste  of  life.  The  benign  process  of 
repair  cannot  go  on,  to  any  extent,  during  strenuous  labor,  but 
by  interposing  frequent  though  brief  periods  of  rest,  we  lessen 
the  amount  of  exhaustion,  refresh  the  jaded  nerves,  and  the 
remaining  labor  is  more  easily  endured. 

285.  Benefits  of  Rest.  There  is  too  little  repose  in  our 
American  nature  and  in  our  modes  of  life.  A  sense  of  fatigue 
is  the  mute  appeal  of  the  body  for  a  brief  respite  from  labor, 
and  the  appeal  should,  if  possible,  be  heeded.  If  this  appeal 
be  not  met,  the  future  exertion  exhausts  far  more  than  if  the 
body  had  been  even  slightly  refreshed.  If  the  appeal  be  met, 
the  brief  mid-labor  rest  eases  the  friction  of  toil,  and  the 
remaining  labor  is  more  easily  borne.  The  feeling  that  a  five- 
minute  rest  is  so  much  time  lost  is  quite  an  error.  It  is  a 
gain  of  physical  strength,  of  mental  vigor,  and  of  the  total 
amount  of  work  done. 

The  merchant  burdened  with  the  cares  of  business  life,  the 
soldier  on  the  long  march,  the  ambitious  student  over-anxious 
to  win  success  in  his  studies,  the  housewife  wearied  with  her 
many  hours  of  exacting  toil,  each  would  make  the  task 
lighter,  and  would  get  through  it  with  less  loss  of  vital  force, 
by  occasionally  devoting  a  few  minutes  to  absolute  rest  in 
entire  relaxation  of  the  strained  muscles  and  overtaxed 
nerves. 


2QO  PRACTICAL  PHYSIOLOGY. 

286.  The  Sabbath  as  a  Day  of  Physiological  Rest.     The 
divine  institution  of  a  Sabbath  of  rest,  one  day  in  seven,  is 
based  upon  the  highest  needs  of  our  nature.    Rest,  to  be  most 
effective,  should  alternate  in  brief  periods  with  labor. 

It  is  sound  physiology,  as  well  as  good  morals  and  manners, 
to  cease  from  the  usual  routine  of  six  days  of  mental  or  physi- 
cal work,  and  rest  both  the  mind  and  the  body  on  the  seventh. 
Those  who  have  succeeded  best  in  what  they  have  undertaken, 
and  who  have  enjoyed  sound  health  during  a  long  and  useful 
life,  have  studiously  lived  up  to  the  mandates  of  this  great 
physiological  law.  It  is  by  no  means  certain  that  the  tendency 
nowadays  to  devote  the  Sabbath  to  long  trips  on  the  bicycle, 
tiresome  excursions  by  land  and  sea,  and  sight-seeing  gen- 
erally, affords  that  real  rest  from  a  physiological  point  of 
view  which  nature  demands  after  six  days  of  well-directed 
manual  or  mental  labor. 

287.  The  Significance  of  Sleep  as  a  Periodical  Rest.     Of 

the  chief  characteristics  of  all  living  beings  none  is  so  signifi- 
cant as  their  periodicity.  Plants  as  well  as  animals  exhibit 
this  periodic  character.  Thus  plants  have  their  annual  as  well 
as  daily  periods  of  activity  and  inactivity.  Hibernating  ani- 
mals pass  the  winter  in  a  condition  of  unconsciousness  only  to 
have  their  functions  of  activity  restored  in  early  spring.  Human 
beings  also  present  many  instances  of  a  periodic  character, 
many  of  which  have  been  mentioned  in  the  preceding  pages. 
Thus  we  have  learned  that  the  heart  has  its  regular  alternating 
periods  of  work  and  rest.  After  every  expiration  from  the 
lungs  there  is  a  pause  before  the  next  inspiration  begins. 

Now  sleep  is  just  another  manifestation  of  this  periodic  and 
physiological  rest  by  which  Nature  refreshes  us.  It  is  during 
the  periods  of  sleep  that  the  energy  expended  in  the  activities 
of  the  waking  hours  is  mainly  renewed.  In  our  waking  moments 
the  mind  is  kept  incessantly  active  by  the  demands  made  on  it 


THE    NERVOUS    SYSTEM.  2QI 

through  the  senses.  There  is  a  never-ceasing  expenditure  of 
energy  and  a  consequent  waste  which  must  be  repaired.  A 
time  soon  comes  when  the  brain  cells  fail  to  respond  to  the 
demand,  and  sleep  must  supervene.  However  resolutely  we 
may  resist  this  demand,  Nature,  in  her  relentless  way,  puts  us  to 
sleep,  no  matter  what  objects  are  brought  before  the  mind  with 
a  view  to  retain  its  attention.1 

288.   Effect  of  Sleep  upon  the  Bodily  Functions.     In  all 

the  higher  animals,  the  central  nervous  system  enters  once  at 
least  in  the  twenty-four  hours  into  the  condition  of  rest  which 
we  call  sleep.  Inasmuch  as  the  most  important  modifications 
of  this  function  are  observed  in  connection  with  the  cerebro- 
spinal  system,  a  brief  consideration  of  the  subject  is  properly 
studied  in  this  chapter.  In  Chapter  IV.  we  learned  that  repose 
was  as  necessary  as  exercise  to  maintain  muscular  vigor.  So 
after  prolonged  mental  exertion,  or  in  fact  any  effort  which 
involves  an  expenditure  of  what  is  often  called  nerve-force, 
sleep  becomes  a  necessity.  The  need  of  such  a  rest  is  self- 
evident,  and  the  loss  of  it  is  a  common  cause  of  the  impairment 
of  health.  While  we  are  awake  and  active,  the  waste  of  the 
body  exceeds  the  repair  ;  but  when  asleep,  the  waste  is  dimin- 
ished, and  the  cells  are  more  actively  rebuilding  the  structure 
for  to-morrow's  labor.  The  organic  functions,  such  as  are  under 
the  direct  control  of  the  sympathetic  nervous  system,  —  circula- 
tion, respiration,  and  digestion,  —  are  diminished  in  activity 
during  sleep.  The  pulsations  of  the  heart  and  the  respiratory 

1  Remarkable  instances  are  cited  to  illustrate  the  imperative  demand  .for  sleep. 
Gunner  boys  have  been  known  to  fall  asleep  during  the  height  of  a  naval  battle, 
owing  to  the  fatigue  occasioned  by  the  arduous  labor  in  carrying  ammunition  for 
the  gunner.  A  case  is  reported  of  a  captain  of  a  British  frigate  who  fell  asleep 
and  remained  so  for  two  hours  beside  one  of  the  largest  guns  of  his  vessel,  the  gun 
being  served  vigorously  all  the  time.  Whole  companies  of  men  have  been  known  to 
sleep  while  on  the  march  during  an  arduous  campaign.  Cavalrymen  and  frontiers- 
men have  slept  soundly  in  the  saddle  during  the  exhausting  campaigns  against  the 
Indians. 


2Q2  PRACTICAL    PHYSIOLOGY. 

movements  are  less  frequent,  and  the  circulation  is  slower. 
The  bodily  temperature  is  reduced,  and  the  cerebral  circulation 
is  diminished.  The  eyes  are  turned  upward  and  inward,  and 
the  pupils  are  contracted. 

The  senses  do  not  all  fall  to  sleep  at  once,  but  drop  off  suc- 
cessively :  first  the  sight,  then  the  smell,  the  taste,  the  hearing, 
and  lastly  the  touch.  The  sleep  ended,  they  awake  in  an  in- 
verse order,  touch,  hearing,  taste,  smell,  and  sight. 

289.  The  Amount  of  Sleep  Required.     No  precise  rule  can 
be  laid  down  concerning  the  amount  of   sleep  required.      It 
varies  with  age,  occupation,  temperament,  and  climate   to  a 
certain  extent.     An  infant  whose  main  business  it  is  to  grow 
spends  the  greater  part  of  its  time   in   sound  sleep.     Adults 
of   average  age  who  work  hard  with   their   hands   or   brain, 
under  perfectly  normal  physiological  conditions,  usually  require 
at  least  eight  hours  of  sleep.     Some  need  less,  but  few  require 
more.      Personal   peculiarities,  and  perhaps  habit  to  a  great 
extent,  exert  a  marked  influence.     Some  of  the  greatest  men, 
as  Napoleon  I.,  have  been  very  sparing  sleepers.     Throughout 
his  long  and  active  life,  Frederick  the  Great  never  slept  more 
than  five  or  six  hours  in  the  twenty-four.     On  the  other  hand, 
some  of  the  busiest  brain-workers  who  lived  to  old   age,  as 
William  Cullen  Bryant  and  Henry  Ward  Beecher,  required  and 
took  care  to  secure  at  least  eight  or  nine  hours  of  sound  sleep 
every  night. 

In  old  age,  less  sleep  is  usually  required  than  in  adult  life, 
while  the  aged  may  pass  much  of  their  time  in  sleep.  In  fact, 
each  person  learns  by  experience  how  much  sleep  is  necessary. 
There  is  no  one  thing  which  more  unfits  one  for  prolonged 
mental  or  physical  effort  than  the  loss  of  natural  rest. 

290.  Practical  Rules  about  Sleep.    Children  should  not  be 
played  with  boisterously  just  before  the  bedtime  hour,  nor  their 


THE    NERVOUS    SYSTEM. 


293 


minds  excited  with  weird  goblin  stories,  or  a  long  time  may  pass 
before  the  wide-open  eyes  and  agitated  nerves  become  com- 
posed to  slumber.  Disturbed  or  insufficient  sleep  is  a  potent 
factor  towards  producing  a  fretful,  irritable  child. 

At  all  ages  the  last  hour  before  sleep  should,  if  possible,  be 
spent  quietly,  to  smooth  the  way  towards  sound  and  refreshing 
rest.  The  sleep  in- 
duced by  medicine  is 
very  often  troubled 
and  unsatisfactory. 
Medicines  of  this  sort 
should  not  be  taken 
except  on  the  advice 
of  a  physician. 

While  a  hearty  meal 
should  not  usually  be 
taken  just  before  bed- 
time, it  is  not  well  to 
go  to  bed  with  a  sense 
of  positive  faintness 
and  hunger.  Rather, 
one  should  take  a  very 
light  lunch  of  quite 
simple  food  as  a  sup- 
port for  the  next  eight 
hours. 

It   is   better,   as   a 

rule,  not  to  engage  in          FlG-  122.  — Trunk  of  the  Left  Pneumogastric. 
Severe     Study     during    (Showing  its  distribution  by  its  branches  and  ganglia 
.    ,     ,  to  the  larynx,  pharynx,  heart,  lungs,  and  other  parts.) 

the  hours  just  before 

bedtime.  Neither  body  nor  mind  being  at  its  best  after  the 
fatigues  of  the  day,  study  at  that  time  wears  upon  the  system 
more,  and  the  progress  is  less  than  at  earlier  hours.  One  hour 
of  morning  or  day  study  is  worth  a  much  longer  time  late  at 


294  PRACTICAL    PHYSIOLOGY. 

night.  It  is,  therefore,  an  economy  both  of  time  and  of  nerve 
force  to  use  the  day  hours  and  the  early  evening  for  study. 

The  so-called  "  cat  naps  "  should  never  be  made  to  serve  as 
a  substitute  for  a  full  night's  sleep.  They  are  largely  a  matter 
of  habit,  and  are  detrimental  to  some  as  well  as  beneficial  to 
others.  Late  hours  are  usually  associated  with  exposure, 
excitement,  and  various  other  drains  upon  the  nerve  force,  and 
hence  are  injurious. 

It  is  better  to  sleep  on  one  or  other  side  than  on  the  back. 
The  head  should  be  somewhat  raised,  and  a  mattress  is  better 
than  a  feather  bed.  The  bedclothes  should  be  sufficient,  but 
riot  too  heavy.  Light  tends  to  prevent  sleep,  as  do  loud  or 
abrupt  sounds,  but  monotonous  sounds  aid  it. 

291.  Alcohol  and  the  Brain.  The  unfortunate  effects  which 
alcoholic  drinks  produce  upon  the  brain  and  nervous  system 
differ  from  the  destructive  results  upon  other  parts  of  the  body 
in  this  respect,  that  elsewhere  the  consequences  are  usually 
both  less  speedy  and  less  obvious.  The  stomach,  the  liver, 
and  even  the  heart  may  endure  for  a  while  the  trespass  of  the 
narcotic  poison,  and  not  betray  the  invasion.  But  the  nervous 
system  cannot,  like  them,  suffer  in  silence. 

In  the  other  parts  of  the  body  the  victim  may  (to  a  certain 
extent)  conceal  from  others  the  suffering  of  which  he  himself 
is  painfully  conscious.  But  the  tortured  brain  instantly  reveals 
the  calamity  and  the  shame,  while  the  only  one  who  may  not 
fully  realize  it  is  the  victim  himself.  Besides  this,  the  injuries 
inflicted  upon  other  organs  affect  only  the  body,  but  here  they 
drag  down  the  mind,  ruin  the  morals,  and  destroy  the  character. 

The  brain  is  indeed  the  most  important  organ  of  the  body, 
as  it  presides  over  all  the  others.  It  is  the  lofty  seat  of  power 
and  authority.  Here  the  king  is  on  his  throne.  But  if,  by 
this  malignant  adversary,  the  -  king  himself  be  dethroned,  his 
whole  empire  falls  to  ruins. 


THE    NERVOUS    SYSTEM.  2Q5 

292.  How  Alcohol  Injures  the  Brain.  The  brain,  the  nerve 
centers,  and  the  nerves  are  all  made  up  of  nerve  pulp,  the  soft- 
est and  most  delicate  tissue  in  the  whole  bodily  structure. 
Wherever  this  fragile  material  occurs  in  our  bodies, — in  the 
skull,  the  spine,  the  trunk,  or  the  limbs,  —  the  all-wise  Architect 
has  carefully  protected  it  from  violence,  for  a  rough  touch  would 
injure  it,  or  even  tender  pressure  would  disturb  its  function. 

It  is  a  further  indication  of  the  supreme  importance  of  the 
brain,  that  about  one-fifth  of  the  entire  blood  of  the  body  is 
furnished  to  it.  Manifestly,  then,  this  vital  organ  must  be 
tenderly  cared  for.  It  must  indeed  be  well  nourished,  and 
therefore  the  blood  sent  to  it  must  be  highly  nutrient,  capable 
of  supplying  oxygen  freely.  This  condition  is  essential  to  suc- 
cessful brain  action.  But  intoxicants  bring  to  it  blood  sur- 
charged with  a  poisonous  liquid,  and  bearing  only  a  limited 
supply  of  oxygen. 

Another  condition  of  a  healthy  brain  is  that  the  supply  of 
blood  to  it  -shall  be  equable  and  uniform.  But  under  the 
influence  of  strong  drink,  the  blood  pours  into  the  paralyzed 
arteries  a  surging  tide  that  floods  the  head,  and  hinders  and 
may  destroy  the  use  of  the  brain  and  the  senses.  Still  another 
requirement  is  that  whatever  is  introduced  into  the  cerebral  tis- 
sues, having  first  passed  through  the  stomach  walls  and  thence 
into  the  blood,  shall  be  bland,  not  irritating.  But  in  the 
brain  of  the  inebriate  are  found  not  only  the  distinct  odor  but 
the  actual  presence  of  alcohol.  Thus  we  plainly  see  how  all 
these  three  vital  conditions  of  a  healthy  brain  are  grossly  vio- 
lated by  the  use  of  intoxicants. 

"  I  think  there  is  a  great  deal  of  injury  being  done  by  the  use  of  alcohol  in  what 
is  supposed  by  the  consumer  to  be  a  most  moderate  quantity,  to  persons  who  are  not 
in  the  least  intemperate,  and  to  people  supposed  to  be  fairly  well.  It  leads  to  degen- 
eration of  the  tissues;  it  damages  the  health;  it  injures  the  intellect.  Short  of 
drunkenness,  that  is,  in  those  effects  of  it  which  stop  short  of  drunkenness,  I  should 
say  from  my  experience  that  alcohol  is  the  most  destructive  agent  we  are  aware  of  in 
this  country."  —  SIR  WILLIAM  GULL,  the  most  eminent  English  physician  of  our  time. 


296  PRACTICAL  PHYSIOLOGY. 

293.  Why  the  Brain   Suffers  from  the  Alcoholic  Habit. 
We  do  not  find  that  the  alcoholic  habit  has  produced  in  the 
brain  the  same  coarse  injuries  that  we  see  in  other  organs,  as 
in  the  stomach,  the  liver,  or  the  heart.     Nor  should  we  expect 
to  find  them  ;  for  so  delicate  and  so  sensitive  is  the  structure 
of  this  organ,  that  a  very  slight  injury  here  goes  a  great  way, 

—  a  disturbance  may  be  overwhelming  to  the  brain  that  would 
be  only  a  trifle  to  some  of  the  less  delicate  organs. 

Alcohol  has  different  degrees  of  affinity  for  different  organs 
of  the  body,  but  much  the  strongest  for  the  cerebral  tissues. 
Therefore  the  brain  feels  more  keenly  the  presence  of  alcohol 
than  does  any  other  organ.  Almost  the  moment  that  the 
poison  is  brought  into  the  stomach,  the  nerves  send  up  the 
alarm  that  an  invading  foe  has  come.  At  once  there  follows 
a  shock  to  the  brain,  and  very  soon  its  paralyzed  blood- 
vessels are  distended  with  the  rush  of  blood.  This  first  effect 
is,  in  a  certain  sense,  exhilarating,  and  from  this  arousing 
influence  alcohol  has  been  erroneously  considered  a  stimulant; 
but  the  falsity  of  this  view  is  pointed  out  elsewhere  in  this 
book. 

294.  Alcohol,  the  Enemy  of  Brain  Work.     The  healthy 
brain  contains  a  larger  proportion  of  water  than  does  any  other 
organ.     Now  alcohol,  with  its  intense  affinity  for  water,  absorbs 
it  from  the  brain,  and  thus  condenses  and  hardens  its  struc- 
ture.    One  of  the  important  elements  of  the  brain  is  its  albu- 
men ;  this  also  is  contracted  by  alcohol.     The  nerve  cells  and 
fibers  gradually  become  shriveled  and  their  activity  is  lowered, 
the   elasticity  of  the   arteries   is    diminished,  the   membranes 
enveloping  the  brain  are  thickened,  and  thus  all  proper  brain 
nutrition  is  impaired.     The   entire  organ  is  slowly  hardened, 
and  becomes  unfitted  for  the  proper  performance  of  its  delicate 
duties.     In  brief,  alcohol  in  any  and  every  form  is  the  enemy 
of  successful  and  long-continued  brain  work. 


THE    NERVOUS    SYSTEM. 


297 


295.  Other  Physical  Results  of 
Intoxicants.  What  are  some  of  the 
physical  results  observed  ?  First, 
we  note  the  failure  of  the  vaso- 
motor  nerves  to  maintain  the  proper 
tone  of  the  blood-vessels,  as  in  the 
turgid  face  and  the  congested  cornea 
of  the  eye.  Again,  we  observe  the 
loss  of  muscular  control,  as  is  shown 
by  the  drop  of  the  lower  lip,  the 
thickened  speech,  and  the  wander- 
ing eye.  The  spinal  cord,  too,  is 
often  affected  and  becomes  unable 
to  respond  to  the  demand  for  reflex 
action,  as  appears  from  the  trem- 
bling hands,  the  staggering  legs,  the 
swaying  body,  and  the  general  mus- 
cular uncertainty.  All  these  are 
varied  results  of  the  temporary  pa- 
ralysis of  the  great  nerve  centers. 

Besides,  the  sensibility  of  the 
nerves  is  deadened.  The  inebriate 
may  seize  a  hot  iron  and  hardly 
know  it,  or  wound  his  hand  pain- 
fully and  never  feel  the  injury.  The 
numbness  is  not  of  the  skin,  but 
of  the  brain,  for  the  drunken  man 
may  be  frozen  or  burned  to  death 
without  pain.  The  senses,  too, 
are  invaded  and  dulled.  Double 
vision  is  produced,  the  eyes  not 
being  so  controlled  as  to  bring  the 
image  upon  corresponding  points 
of  the  retina. 


FIG.  123. —  Nerve  Trunks  of  the 
Right  Arm. 


298  PRACTICAL    PHYSIOLOGY. 

296.  Diseases  Produced  by  Alcohol.     The  diseases  that 
follow  in  the  train  of  the  alcoholic  habit  are  numerous   and 
fatal.     It  lays  its  paralyzing   hand  upon  the  brain  itself,  and 
soon  permanently  destroys  the   integrity  of  its  functions.     In 
some  the  paralysis  is  local  only,  perhaps  in  one  of  the  limbs,  or 
on  one  side  of  the  body ;  in  others  there  is  a  general  muscular 
failure.     The  vitality  of  the   nerve  centers   is  so  thoroughly 
impaired  that  general  paralysis  often  ensues.     A  condition  of 
insomnia,  or  sleeplessness,  often  follows,  or  when  sleep  does 
come,  it  is  in  fragments,  and  is  far  from  refreshing  to  the 
jaded  body. 

In  time  follows  another  and  a  terrible  disease  known  as 
delirium  tremens;  and  this  may  occur  in  those  who  claim  to  be 
only  moderate  drinkers,  rarely  if  ever  intoxicated.  It  accom- 
panies an  utter  breakdown  of  the  nervous  system.  Here 
reason  is  for  the  time  dethroned,  while  at  some  times  wild  and 
frantic,  or  at  others  a  low,  mumbling  delirium  occurs,  with  a 
marked  trembling  from  terror  and  exhaustion. 

There  is  still  another  depth  of  ruin  in  this  downward  course, 
and  that  is  insanity.  In  fact,  every  instance  of  complete  intox- 
ication is  a  case  of  temporary  insanity,  that  is,  of  mental  un- 
soundness  with  loss  of  self-control.  Permanent  insanity  may 
be  one  of  the  last  results  of  intemperance.  Alcoholism  sends 
to  our  insane  asylums  a  large  proportion  of  their  inmates,  as 
ample  records  testify. 

297.  Mental    and   Moral  Ruin  Caused    by  Alcoholism. 

Alcoholism,  the  evil  prince  of  destroyers,  also  hastens  to  lay 
waste  man's  mental  and  moral  nature.  Just  as  the  inebriate's 
senses,  sight,  hearing,  and  touch,  fail  to  report  correctly  of  the 
outer  world,  so  the  mind  fails  to  preside  properly  over  the 
inner  realm.  Mental  perceptions  are  dulled.  The  stupefied 
faculties  can  hardly  be  aroused  by  any  appeal.  Memory  fails. 
Thus  the  man  is  disqualified  for  any  responsible  labor.  No 


THE    NERVOUS    SYSTEM.  299 

railroad  company,  no  mercantile  house,  will  employ  any  one 
addicted  to  drinking.  The  mind  of  the  drunkard  is  unable  to 
retain  a  single  chain  of  thought,  but  gropes  about  with  idle 
questionings.  The  intellect  is  debased.  Judgment  is  impossi- 
ble, for  the  unstable  mind  cannot  think,  compare,  or  decide. 

The  once  active  power  of  the  will  is  prostrate,  and  the  victim 
can  no  longer  resist  the  feeblest  impulse  of  temptation.  The 
grand  faculty  of  self-control  is  lost  ;  and  as  a  result,  the  baser 
instincts  of  our  lower  nature  are  now  uppermost ;  greed  and 
appetite  rule  unrestrained. 

But  the  moral  power  is  also  dragged  down  to  the  lowest 
depths.  All  the  finer  sensibilities  of  character  are  deadened  ; 
all  pride  of  personal  appearance,  all  nice  self-respect  and 
proper  regard  for  the  good  opinion  of  others,  every  sense  of 
decorum,  and  at  last  every  pretence  of  decency.  Dignity  of 
behavior  yields  to  clownish  silliness,  and  the  person  lately  re- 
spected is  now  an  object  of  pity  and  loathing.  The  great 
central  convictions  of  right  and  wrong  now  find  no  place  in 
his  nature  ;  conscience  is  quenched,  dishonesty  prevails.  This 
is  true  both  as  to  the  solemn  promises,  which  prove  mere 
idle  tales,  and  also  as  to  property,  for  he  resorts  to  any  form 
of  fraud  or  theft  to  feed  the  consuming  craving  for  more 
drink. 

298.  Evil  Results  of  Alcoholism  Inherited.  But  the  calam- 
ity does  not  end  with  the  offender.  It  may  follow  down  the 
family  line,  and  fasten  itself  upon  the  unoffending  children. 
These  often  inherit  the  craving  for  drink,  with  the  enfeebled 
nature  that  cannot  resist  the  craving,  and  so  are  almost  inev- 
itably doomed  to  follow  the  appalling  career  of  their  parents 
before  them. 

Nor  does  this  cruel  taint  stop  with  the  children.  Even  their 
descendants  are  often  prone  to  become  perverse.  As  one 
example,  careful  statistics  of  a  large  number  of  families,  more 


3OO  PRACTICAL    PHYSIOLOGY. 

than  two  hundred  descended  from  drunkards,  show  that  a.  very 
large  portion  of  them  gave  undoubted  proof  of  well-marked 
degeneration.  This  was  plain  in  the  unusual  prevalence  of 
infant  mortality,  convulsions,  epilepsy,  hysteria,  fatal  brain 
diseases,  and  actual  imbecility.1 

It  is  found  that  the  long-continued  habitual  user  of  alcoholic 
drinks,  the  man  who  is  never  intoxicated,  but  who  will  tell  you 
that  he  has  drunk  whiskey  all  his  life  without  being  harmed  by 
it,  is  more  likely  to  transmit  the  evil  effects  to  his  children  than 
the  man  who  has  occasional  drunken  outbreaks  with  intervals 
of  perfect  sobriety  between.  By  his  frequently  repeated  small 
drams  he  keeps  his  tissues  constantly  "  alcoholized  "  to  such  an 
extent  that  they  are  seldom  free  from  some  of  the  more  or  less 
serious  consequences.  His  children  are  born  with  organisms 
which  have  received  a  certain  bias  from  which  they  cannot 
escape ;  they  are  freighted  with  some  heredity,  or  predispo- 
sition to  particular  forms  of  degeneration,  to  some  morbid 
tendency,  to  an  enfeebled  constitution,  to  various  defective 
conditions  of  mind  and  body.  Let  the  children  of  such  a  man 
attempt  to  imitate  the  drinking  habits  of  the  father  and  they 
quickly  show  the  effects.  Moderate  drinking  brings  them 
down. 

Among  other  consequences  of  an  alcoholic  inheritance  which 
have  been  traced  by  careful  observers  are  :  Morbid  changes  in 

1  According  to  the  Annual  Report  of  New  York  State  Reformatory,  for  1896, 
drunkenness  among  the  inmates  can  be  clearly  traced  to  no  less  than  38  per  cent  of 
the  fathers  and  mothers  only. 

Drunkenness  among  the  parents  of  38  per  cent  of  the  prisoners  in  a  reformatory 
of  this  kind  is  a  high  and  a  serious  percentage.  It  shows  that  the  demoralizing 
influence  of  drink  is  apt  to  destroy  the  future  of  the  child  as  well  as  the  character  of 
the  parent. 

"  There  is  a  marked  tendency  in  nature  to  transmit  all  diseased  conditions.  Thus 
the  children  of  consumptive  parents  are  apt  to  be  consumptive.  But,  of  all  agents, 
alcohol  is  the  most  potent  in  establishing  a  heredity  that  exhibits  itself  in  the 
destruction  of  mind  and  body.  There  is  not  only  a  propensity  transmitted,  but  an 
actual  disease  of  the  nervous  system."  —  DR.  WILLA.RD  PARKER. 


THE    NERVOUS    SYSTEM.  3<DI 

the  nerve  centers,  consisting  of  inflammatory  lesions,  which 
vary  according  to  the  age  in  which  they  occur;  alcoholic 
insanity ;  congenital  malformations  ;  and  a  much  higher  infant 
death  rate,  owing  to  lack  of  vitality,  than  among  the  children 
of  normal  parents. 

Where  the  alcoholic  inheritance  does  not  manifest  itself  in 
some  definite  disease  or  disorder,  it  can  still  be  traced  in  the 
limitations  to  be  found  in  the  drinking  man's,  descendants. 
They  seem  to  reach  a  level  from  which  they  cannot  ascend, 
and  where  from  slight  causes  they  deteriorate.  The  parents, 
by  alcoholic  poisoning,  have  lowered  the  race  stock  of  vitality 
beyond  the  power  of  ascent  or  possibility  to  rise  above  or  over- 
come the  downward  tendency. 

Of  course  these  effects  of  alcoholics  differ  widely  according 
to  the  degree  of  intoxication.  Yet,  we  must  not  forget  that 
the  real  nature  of  inebriety  is  always  the  same.  The  end  dif- 
fers from  the  beginning  only  in  degree.  He  who  would  avoid 
a  life  of  sorrow,  disgrace,  and  shame  must  carefully  shun  the 
very  first  glass  of  intoxicants. 

299.  Opium.     Opium  is   a  gum-like   substance,   the   dried 
juice  of  the  unripe  capsule  of  the  poppy.     The  head  of  the 
plant  is  slit  with  fine  incisions,  and  the  exuding  white  juice  is 
collected.     When  it  thickens  and  is  moulded  in  mass,  it  be- 
comes dark  with  exposure.     Morphine,  a  white   powder,  is  a 
very  condensed  form  of  opiate ;    laudanum,  an  alcoholic  solu- 
tion of  marked  strength;  and  paregoric,  a  diluted  and  flavored 
form  of  alcoholic  tincture. 

300.  Poisonous  Effects  of  Opium.     Some  persons  are  drawn 
into  the  use  of  opium,  solely  for  its  narcotic  and  intoxicating 
influence.     Every  early  consent  to  its  use  involves  a  lurking 
pledge  to  repeat  the  poison,  till  soon  strong  cords  of  the  intox- 
icant appetite  bind  the  now  yielding  victim. 


3O2  PRACTICAL    PHYSIOLOGY. 

Opium  thus  used  lays  its  benumbing  hand  upon  the  brain, 
the  mind  is  befogged,  thought  and  reasoning  are  impossible. 
The  secretions  of  the  stomach  are  suspended,  digestion  is 
notably  impaired,  and  the  gastric  nerves  are  so  deadened  that 
the  body  is  rendered  unconscious  of  its  needs. 

The  moral  sense  is  extinguished,  persons  once  honest  resort 
to  fraud  and  theft,  if  need  be,  to  obtain  the  drug,  till  at  last 
health,  character,  and  life  itself  all  become  a  pitiful  wreck. 

301.  The  Use  of  Opium  in  Patent  Medicines.     Some  forms 
of  this  drug  are  found  in  nearly  all  the  various  patent  medi- 
cines  so  freely  sold  as  a  cure-all  for  every  mortal  disease. 
Opiates  are  an  ingredient  in  different  forms  and  proportions 
in   almost   all   the   soothing-syrups,   cough  medicines,  cholera 
mixtures,   pain   cures,   and   consumption    remedies,  so  widely 
and  unwisely  used.     Many  deaths  occur  from  the  use  of  these 
opiates,  which  at  first  seem  indeed  to  bring  relief,  but  really 
only  smother  the  prominent  symptoms,  while  the  disease  goes 
on  unchecked,  and  at  last  proves  fatal. 

These  patent  medicines  may  appear  to  help  one  person  and 
be  fraught  with  danger  to  the  next,  so  widely  different  are 
the  effects  of  opiates  upon  different  ages  and  temperaments. 
But  it  is  upon  children  that  these  fatal  results  oftenest  fall. 
Beyond  doubt,  thousands  of  children  have  been  soothed  and 
soothed  out  of  existence.1 

302.  The  Victim  of  the  Opium  Habit.     Occasionally  per- 
sons convalescing  from  serious  sickness  where  anodynes  were 
taken,   unwisely  cling  to  them   long   after   recovery.      Other 
persons,   jaded  with  business   or  with  worry,  and  unable   to 
sleep,  unwisely  resort  to  some  narcotic  mixture  to  procure  rest. 
In  these  and  other  similar  cases,  the  use  of  opiates  is  always 

1  "  It  is  very  certain  that  many  infants  annually  perish  from  this  single  cause." — 
REESE'S  Manual  of  Toxicology. 


THE    NERVOUS    SYSTEM.  303 

most  pernicious.  The  amount  must  be  steadily  increased  to 
obtain  the  elusive  repose,  and  at  best  the  phantom  too  often 
escapes. 

Even  if  the  desired  sleep  is  procured,  it  is  hardly  the  coveted 
rest,  but  a  troubled  and  dreamy  slumber,  leaving  in  the  morn- 
ing the  body  quite  unrefreshed,  the  head  aching,  the  mouth 
dry,  and  the  stomach  utterly  devoid  of  appetite.  But  far 
worse  than  even  this  condition  is  the  slavish  yielding  to  the 
habit,  which  soon  becomes  a  bondage  in  which  life  is  shorn  of 
its  wholesome  pleasures,  and  existence  becomes  a  burden. 

303.  Chloral.     There   are  other  preparations  which  have 
become  instruments  of  direful  and  often  fatal  injury.     Chloral 
is  a  powerful  drug  that  has  been  much  resorted  to  by  unthink- 
ing persons  to  produce  sleep.     Others,  yielding  to  a  morbid 
reluctance  to  face  the  problems  of  life,  have  timidly  sought 
shelter  in   artificial  forgetfulness.     To   all  such   it  is  a  false 
friend.     Its   promises    are   treason.      It   degrades   the    mind, 
tramples  upon  the  morals,  overpowers  the  will,  and  destroys 
life  itself. 

304.  Cocaine,   Ether,   Chloroform,   and  Other  Powerful 
Drugs.      Another   dangerous   drug   is   Cocaine.      Ether  and 
chloroform,  those  priceless  blessings  to  the  human   race  if 
properly  controlled,  become  instruments  of  death  when  care- 
lessly trifled  with.     Persons  who  have  been   accustomed   to 
inhale  the  vapor  in  slight  whiffs  for  neuralgia  or  similar  trou- 
bles do  so  at  imminent  hazard,  especially  if  lying  down.     They 
are  liable  to  become  sfowly  unconscious,  and  so  to  continue 
the  inhalation  till  life  is  ended. 

There  is  still  another  class  of  drugs  often  carelessly  used, 
whose  effect,  while  less  directly  serious  than  those  mentioned, 
is  yet  far  from  harmless.  These  drugs,  which  have  sprung 
into  popular  use  since  the  disease  la  grippe  began  its  dreaded 
career,  include  phenacetine,  antipyrine,  antifebrine,  and  other 


304  PRACTICAL  PHYSIOLOGY. 

similar  preparations.  These  drugs  have  been  seized  by  the 
public  and  taken  freely  and  carelessly  for  all  sorts  and  condi- 
tions of  trouble.  The  random  arrow  may  yet  do  serious  harm. 
These  drugs,  products  of  coal-oil  distillation,  are  powerful 
depressants.  They  lower  the  action  of  the  heart  and  the  tone 
of  the  nervous  centers.  Thus  the  effect  of  their  continued  use 
is  to  so  diminish  the  vigor  of  the  system  as  to  aggravate  the 
very  disorder  they  are  taken  to  relieve. 

305.  Effect  of  Tobacco  on  the  Nervous  System.  That  the 
use  of  tobacco  produces  a  pernicious  effect  upon  the  nervous 
system  is  obvious  from  the  indignant  protest  of  the  entire  body 
against  it  when  it  is  first  used.  Its  poisonous  character  is 
amply  shown  by  the  distressing  prostration  and  pallor,  the 
dizziness  and  faintness,  with  extreme  nausea  and  vomiting, 
which  follow  its  employment  by  a  novice. 

The  morbid  effects  of  tobacco  upon  the  nervous  system  of 
those  who  habitually  use  it  are  shown  in  the  irregular  and 
enfeebled  action  of  the  heart,  with  dizziness  and  muscular 
tremor.  The  character  of  the  pulse  shows  plainly  the  un- 
steady heart  action,  caused  by  partial  paralysis  of  the  nerves 
controlling  this  organ.  Old,  habitual  smokers  often  show  an 
irritable  and  nervous  condition,  with  sleeplessness,  due  doubt- 
less to  lack  of  proper  brain  nutrition. 

All  these  results  tend  to  prove  that  tobacco  is  really  a  nerve 
poison,  and  there  is  reason  to  suspect  that  the  nervous  break- 
down of  many  men  in  mature  life  is  often  due  to  the  continued 
use  of  this  depressing  agent.  This  is  shown  more  especially 
in  men  of  sedentary  life  and  habits,  as  men  of  active  habits 
and  out-door  life,  experience  less  of  the  ill  effects  of  tobacco. 

Few,  if  any,  habitual  users  of  tobacco  ever  themselves  approve 
of  it.  They  all  regret  the  habit,  and  many  lament  they  are  so 
enslaved  to  it  that  they  cannot  throw  it  off.  They  very  rarely 
advise  any  one  to  follow  their  example. 


THE    NERVOUS    SYSTEM.  305 

306.  Effects  of  Tobacco  on  the  Mind.     With  this  continu- 
ously depressing  effect   of  tobacco  upon  the  brain,  it   is  little 
wonder   that   the  mind  may  become  enfeebled  and  lose  its 
capacity  for  study  or  successful  effort.     This  is  especially  true 
of   the   young.     The  growth   and  development  of  the  brain 
having  been  once  retarded,  the  youthful  user  of  tobacco  (espe- 
cially the  foolish  cigarette-smoker)  has  established  a  permanent 
drawback  which  may  hamper  him  all  his  life. 

The  young  man  addicted  to  the  use  of  tobacco  is  often 
through  its  use  retarded  in  his  career  by  mental  languor  or 
weakening  will  power,  and  by  mental  incapacity.  The  keen- 
ness of  mental  perception  is  dulled,  and  the  ability  to  seize 
and  hold  an  abstract  thought  is  impaired.  True,  these  effects 
are  not  sharply  obvious,  as  it  would  be  impossible  to  contrast 
the  present  condition  of  any  one  person  with  what  it  might 
have  been.  But  the  comparison  of  large  numbers  conveys  an 
instructive  lesson.  Scholars  who  start  well  and  give  promise 
of  a  good  future  fail  by  the  way.  The  honors  of  the  great 
schools,  academies,  and  colleges  are  very  largely  taken  by  the 
tobacco  abstainers.  This  is  proved  by  the  result  of  repeated 
and  extensive  comparisons  of  the  advanced  classes  in  a  great 
number  of  institutions  in  this  country  and  in  Europe.  So  true 
is  this  that  any  young  man  who  aspires  to  a  noble  career  should 
bid  farewell  either  to  his  honorable  ambition  or  to  his  tobacco, 
for  the  two  very  rarely  travel  together.  Consequently  our  mili- 
tary and  naval  academies  and  very  many  seminaries  and  col- 
leges prohibit  the  use  of  tobacco  by  their  students.  For  the 
same  reasons  the  laws  of  many  states  very  properly  forbid  the 
sale  to  boys  of  tobacco,  and  especially  of  cigarettes. 

307.  Effect  of  Tobacco  upon  Character.     Nor  does  tobacco 
spare  the  morals.     The  tobacc9~user  is  apt  to  manifest  a  self- 
ish disregard  of  the  courtesies  due  to  others.     He  brings  to 
the  presence  of  others  a  repulsive  breath,  and  clothing  tainted 


3O6  PRACTICAL    PHYSIOLOGY. 

with  offensive  odors.  He  poisons  the  atmosphere  that  others 
must  inhale,  and  disputes  their  rights  to  breathe  a  pure,  untainted 
air.  The  free  use  of  tobacco  by  young  people  dulls  the  acute- 
ness  of  the  moral  senses,  often  leads  to  prevarication  and 
deceit  in  the  indulgence,  and  is  apt  to  draw  one  downward  to 
bad  associates.  It  is  not  the  speed  but  the  direction  that  tells 
on  the  future  character  and  destiny  of  young  men. 

ADDITIONAL   EXPERIMENTS. 

Experiment  132.  To  illustrate  the  cooperation  of  certain  parts  of  the 
body.  Tickle  the  inside  of  the  nose  with  a  feather.  This  does  not  inter- 
fere with  the  muscles  of  breathing,  but  they  come  to  the  help  of  the 
irritated  part,  and  provoke  sneezing  to  clear  and  protect  the  nose. 

Experiment  133.  Pretend  to  aim  a  blow  at  a  person's  eye.  Even  if  he 
is  warned  beforehand,  the  lids  will  close  in  spite  of  his  effort  to  prevent 
them. 

Experiment  134.  To  illustrate  how  sensations  are  referred  to  the  ends  of 
the  nerves.  Strike  the  elbow  end  of  the  ulna  against  anything  hard  (com- 
monly called  "  hitting  the  crazy  bone  ")  where  the  ulna  nerve  is  exposed, 
and  the  little  finger  and  the  ring  finger  will  tingle  and  become  numb. 

Experiment  135.  To  show  that  every  nerve  is  independent  of  any  other. 
Press  two  fingers  closely  together.  Let  the  point  of  the  finest  needle  be 
carried  ever  so  lightly  across  from  one  finger  to  another,  and  we  can  easily 
tell  just  when  the  needle  leaves  one  finger  and  touches  the  other. 

Experiment  136.  To  paralyze  a  nerve  temporarily.  Throw  one  arm 
over  the  sharp  edge  of  a  chair-back,  bringing  the  inner  edge  of  the  biceps 
directly  over  the  edge  of  the  chair.  Press  deep  and  hard  for  a  few  min- 
utes. The  deep  pressure  on  the  nerve  of  the  arm  will  put  the  arm 
"  asleep,"  causing  numbness  and  tingling.  The  leg  and  foot  often  "  get 
asleep  "  by  deep  pressure  on  the  nerves  of  the  thigh. 

Experiment  137.  Press  the  ulnar  nerve  at  the  elbow,  the  prickling  sen- 
sation is  referred  to  the  skin  on  the  ulnar  side  of  the  hand. 

Experiment  138.  Dip  the  elbow  in  ice-cold  water;  at  first  one  feels  the 
sensation  of  cold,  owing  to  the  effect  on  the  cutaneous  nerve-endings. 
Afterwards,  when  the  trunk  of  the  ulnar  nerve  is  affected,  pain  is  felt  in 
the  skin  of  the  ulnar  side  of  the  hand,  where  the  nerve  terminates. 


CHAPTER    XI. 
THE    SPECIAL    SENSES. 

308.  The  Special  Senses.     In  man  certain  special  organs 
are  set  apart  the  particular  duty  of  which  is  to  give  information 
of  the  nature  of  the  relations  which  he  sustains  to  the  great 
world  of  things,  and  of  which  he  is  but  a  mere  speck.     The 
special  senses  are  the  avenues  by  which  we  obtain  this  in- 
formation as  to  our  bodily  condition,  the  world  around  us,  and 
the  manner  in  which  it  affects  us. 

Animals  high  in  the  scale  are  affected  in  so  many  different 
ways,  and  by  so  many  agencies,  that  a  subdivision  of  labor 
becomes  necessary  that  the  sense  avenues  may  be  rigidly 
guarded.  One  person  alone  may  be  a  sufficient  watch  on  the 
deck  of  a  sloop,  but  an  ocean  steamer  needs  a  score  or  more 
on  guard,  each  with  his  special  duty  and  at  his  own  post.  Or 
the  senses  are  like  a  series  of  disciplined  picket-guards,  along 
the  outposts  of  the  mind,  to  take  note  of  events,  and  to  report 
to  headquarters  any  information  which  may  be  within  the 
range  of  their  duty. 

Thus  it  is  that  we  are  provided  with  a  number  of  Special 
senses,  by  means  of  which  information  is  supplied  regarding 
outward  forces  and  objects.  These  are  touch,  taste,  smell, 
seeing,  and  hearing,  to  which  may  be  added  the  muscular 
sense  and  a  sense  of  temperature. 

309.  General  Sensations.     The  body,  as  we  have  learned, 
is  made  up  of  a  great  number  of  complicated    organs,  each 
doing  its  own  part  of  the  general  work  required  for  the  life 
and  vigor  of  the  human  organism.     These  organs  should  all 


308  PRACTICAL    PHYSIOLOGY. 

work  in  harmony  for  the  good  of  the  whole.  We  must  have 
some  means  of  knowing  whether  this  harmony  is  maintained, 
and  of  receiving  timely  warning  if  any  organ  fails  to  do  its 
particular  duty. 

Such  information  is  supplied  by  the  common  or  general 
sensations.  Thus  we  have  a  feeling  of  hunger  or  thirst  indi- 
cating the  need  of  food,  and  a  feeling  of  discomfort  when 
imperfectly  clad,  informing  us  of  the  need  of  more  clothing. 

To  these  may  be  added  the  sensation  of  pain,  tickling,  itch- 
ing, and  so  on,  the  needs  of  which  arise  from  the  complicated 
structure  of  the  human  body.  The  great  majority  of  sensations 
result  from  some  stimulus  or  outward  agency ;  and  yet  some 
sensations,  such  as  those  of  faintness,  restlessness,  and  fatigue 
seem  to  spring  up  within  us  in  some  mysterious  way,  without 
any  obvious  cause. 

310.  Essentials  of  a  Sense  Organ.  Certain  essentials  are 
necessary  for  a  sensation.  First,  there  is  a  special  structure 
adapted  to  a  particular  kind  of  influence.  Thus  the  ear  is 
formed  specially  for  being  stimulated  by  the  waves  of  sound, 
while  the  eye  is  not  influenced  by  sound,  but  responds  to  the 
action  of  light.  These  special  structures  are  called  terminal 
organs. 

Again,  a  nerve  proceeds  from  the  special  structure,  which 
is  in  direct  communication  with  nerve  cells  in  the  brain  in 
the  region  of  consciousness.  This  last  point  is  important  to 
remember,  for  if.  on  some  account  the  impression  is  arrested  in 
the  connecting  nerve,  no  sensation  will  result.  Thus  a  man 
whose  spine  has  been  injured  may  not  feel  a  severe  pinch  on 
either  leg.  The  impression  may  be  quite  sufficient  to  stimu- 
late a  nerve  center  in  a  healthy  cord,  so  as  to  produce  a 
marked  reflex  act,  but  he  has  no  sensation,  because  the  injury 
has  prevented  the  impression  from  being  carried  up  the  cord 
to  the  higher  centers  in  the  brain. 


THE  SPECIAL  SENSES.  3OQ 

311.  The  Condition  of  Sensation.     It  is  thus  evident  that 
while  an  impression  may  be  made  upon  a  terminal   organ,  it 
cannot  strictly  be  called  a  sensation  until  the  person  becomes 
conscious  of  it.     The  consciousness  of  an  impression  is,  there- 
fore, the  essential  element  of  a  sensation. 

It  follows  that  sensation  may  be  prevented  in  various  ways. 
In  the  sense  of  sight,  for  example,  one  person  may  be  blind 
because  the  terminal  organ,  or  eye,  is  defective  or  diseased. 
Another  may  have  perfect  eyes  and  yet  have  no  sight,  because 
a  tumor  presses  on  the  nerve  between  the  eye  and  the  brain. 
In  this  case,  the  impression  fails  because  of  the  break  in  the 
communication.  Once  more,  the  eye  may  be  perfect  and  the 
nerve  connection  unbroken,  and  yet  the  person  cannot  see, 
because  the  center  in  the  brain  itself  is  injured  from  disease 
or  accident,  and  cannot  receive  the  impression. 

312.  The  Functions  of  the  Brain  Center  in  the  Perception 
of  an  Impression.     Sensation  is  really  the  result  of  a  change 
which  occurs  in  a  nerve  center  in  the  brain,  and  yet  we  refer 
impressions  to  the  various  terminal  organs.     Thus,  when  the 
skin  is  pinched,  the  sensation  is  referred  to  the  skin,  although 
the  perception  is  in  the  brain.     We  may  think  it  is  the  eyes 
that  see  objects  ;  in  reality,  it  is  only  the  brain  that  takes  note 
of  them. 

This  is  largely  the  result  of  education  and  habit.  From  a 
blow  on  the  head  one  sees  flashes  of  light  as  vividly  as  if 
torches  actually  dance  before  the  eyes.  Impressions  have 
reached  the  seeing-center  in  the  brain  from  irritation  of  the 
optic  nerve,  producing  the  same  effect  as  real  lights  would 
cause.  In  this  case,  however,  knowing  the  cause  of  the  colors, 
the  person  is  able  to  correct  the  erroneous  conclusion. 

As  a  res-alt  of  a  depraved  condition  of  blood,  the  seeing- 
center  itself  may  be  unduly  stimulated,  and  a  person  may  see 
objects  which  appear  real.  Thus  in  an  attack  of  delirium 


3io 


PRACTICAL    PHYSIOLOGY. 


tremens,  the  victim  of  alcoholic  poisoning  sees  horrible  and 
fantastic  creatures.  The  diseased  brain  refers  them  as  usual 
to  the  external  world  ;  hence  they  appear  real.  As  the  suffer- 
er's judgment  is  warped  by  the  alcoholic  liquor,  he  cannot 
correct  the  impressions,  and  is  therefore  deceived  by  them. 

313.  Organs  of  Special  Sense.  The  organs  of  special 
sense,  the  means  by  which  we  are  brought  into  relation  with 
surrounding  objects,  are  usually  classed  as 
five  in  number.  They  are  sometimes  fanci- 
fully called  "  the  five  gateways  of  knowledge  " 
—  the  skin,  the  organ  of  touch ;  the  tongue, 
of  taste ;  the  nose,  of  smell ;  the  eye,  of 
sight;  and  the  ear,  of  hearing. 

314.  The  Organ  of  Touch.  The  organ  of 
touch,  or  tactile  sensibility,  is  the  most  widely 
extended  of  all  the  special  senses,  and  perhaps 
the  simplest.  It  is  certainly  the  most  precise 
and  certain  in  its  results.  It  is  this  sense  to 
which  we  instinctively  appeal  to  escape  from 
the  illusions  into  which  the  other  senses  may 
mislead  us.  It  has  its  seat  in  the  skin  all 
over  the  body,  and  in  the  mucous  membrane  of  the  nostrils. 
All  parts  of  the  body,  however,  do  not  have  this  sense  in  an 
equal  degree. 

In  Chapter  IX.  we  learned  that  the  superficial  layers  of  the 
skin  covers  and  dips  in  between  the  papillae.  We  also  learned 
that  these  papillae  are  richly  provided  with  blood-vessels  and 
sensory  nerve  fibers  (sec.  234).  Now  these  nerve  fibers  termi- 
nate in  a  peculiar  way  in  those  parts  of  the  body  which  are 
endowed  with  a  very  delicate  sense  of  touch.  In  every  papilla 
are  oval-shaped  bodies  about  ^  JT  of  an  inch  long,  around  which 
the  nerve  fibers  wind,  and  which  they  finally  enter.  These  are 
called  touch-bodies,  or  tactile  corpuscles,  and  are  found  in 


FIG.  124. —  Magni- 
fied View  of  a  Pa- 
pilla of  the  Skin, 
with  a  Touch  Cor- 
puscle. 


THE    SPECIAL    SENSES.  311 

great  numbers  on  the  feet  and  toes,  and  more  scantily  in  other 
places,  as  on  the  edges  of  the  eyelids. 

Again,  many  of  the  nerve  fibers  terminate  in  corpuscles,  the 
largest  about  ^  of  an  inch  long,  called  Pacinian  corpuscles. 
These  are  most  numerous  in  the  palm  of  the  hand  and  the  sole 
of  the  foot.  In  the  papillae  of  the  red  border  of  the  lips  the 
nerves  end  in  capsules  which  enclose  one  or  more  fibers,  and 
are  called  end-bulbs. 

The  great  majority  of  the  nerve  fibers  which  supply  the 
skin  do  not  end  in  such  well-defined  organs.  They  oftener 
divide  into  exceedingly  delicate  filaments,  the  terminations  of 
which  are  traced  with  the  greatest  difficulty. 

315.  The  Sense  of  Touch.  Touch  is  a  sensation  of  contact 
referred  to  the  surface  of  the  body.  It  includes  three  things, 
— the  sense  of  contact,  the  sense  of  pressure,  and  the  sense 
of  heat  and  cold. 

The  sense  of  contact  is  the  most  important  element  in  touch. 
By  it  we  learn  of  the  form,  size,  and  other  properties  of  objects, 
as  their  smoothness  and  hardness.  As  we  all  know,  the  sense 
of  touch  varies  in  different  parts  of  the  skin.  It  is  most  acute 
where  the  outer  skin  is  thinnest.  The  tips  of  the  fingers,  the 
edges  of  the  lips,  and  the  tip  of  the  tongue  are  the  most  sensi- 
tive parts. 

Even  the  nails,  the  teeth,  and  the  hair  have  the  sense  of 
touch  in  a  slight  degree.  When  the  scarf  skin  is  removed,  the 
part  is  not  more  sensitive  to  sense  of  contact.  In  fact,  direct 
contact  with  the  unprotected  true  skin  occasions  pain,  which 
effectually  masks  the  feeling  of  touch.  The  sense  of  touch  is 
capable  of  education,  and  is  generally  developed  to  an  extra- 
ordinary degree  in  persons  who  are  deprived  of  some  other 
special  sense,  as  sight  or  hearing.  We  read  of  the  famous 
blind  sculptor  who  was  said  to  model  excellent  likenesses, 
guided  entirely  by  the  sense  of  touch.  An  eminent  authority 


312  PRACTICAL    PHYSIOLOGY. 

on  botany  was  a  blind  man,  able  to  distinguish  rare  plants  by 
the  fingers,  and  by  the  tip  of  the  tongue.  The  blind  learn  to 
read  with  facility  by  passing  their  fingers  over  raised  letters  of 
a  coarse  type.  It  is  impossible  to  contemplate,  even  for  a 
moment,  the  prominence  assigned  to  the  sense  of  touch  in  the 
physical  organism,  without  being  impressed  with  the  manifes- 
tations of  design  —  the  work  of  an  all-wise  Creator. 

316.     Muscular  Sense ;    Sense  of  Temperature ;    Pain. 

When  a  heavy  object  is  laid  upon  certain  parts  of  the  body, 
it  produces  a  sensation  of  pressure.  By  it  we  are  enabled  to 
estimate  differences  of  weight.  If  an  attempt  be  made  to  raise 
this  object,  it  offers  resistance  which  the  muscles  must  over- 
come. This  is  known  as  the  muscular  sense.  It  depends  on 
sensory  nerves  originating  in  the  muscles  and  carrying  impres- 
sions from  them  to  the  nerve  centers. 

The  skin  also  judges,  to  a  certain  extent,  of  heat  and  cold. 
These  sensations  can  be  felt  only  by  the  skin.  Direct  irrita- 
tion of  a  nerve  does  not  give  rise  to  them.  Thus,  the  exposed 
pulp  of  a  diseased  tooth,  when  irritated  by  cold  fluids,  gives 
rise  to  pain,  and  not  to  a  sensation  of  temperature.  Various 
portions  of  the  body  have  different  degrees  of  sensibility  in 
this  respect.  The  hand  will  bear  a  degree  of  heat  which  would 

Experiment  139.  To  illustrate  how  the  sense  of  touch  is  a  matter  of  habit 
or  education.  Shut  both  eyes,  and  let  a  friend  run  the  tips  of  your  fingers 
first  lightly  over  a  hard  plane  surface  ;  then  press  hard,  then  lightly  again, 
and  the  surface  will  seem  to  be  concave. 

Experiment  140.  Cross  the  middle  over  the  index  finger,  roll  a  small 
marble  between  the  fingers  ;  one  has  a  distinct  impression  of  two  marbles. 
Cross  the  fingers  in  the  same  way,  and  rub  them  against  the  point  of  the 
nose.  A  similar  illusion  is  experienced. 

Experiment  141.  To  test  the  sense  of  locality.  Ask  a  person  to  shut 
his  eyes,  touch  some  part  of  his  body  lightly  with  the  point  of  a  pin,  and 
ask  him  to  indicate  the  part  touched. 


THE    SPECIAL    SENSES.  313 

cause  pain  to  some  other  parts  of  the  body.  Then,  again, 
the  sensibility  of  the  outer  skin  seems  to  affect  the  sensibility 
to  heat,  for  parts  with  a  thin  skin  can  bear  less  heat  than 
portions  with  a  thick  cuticle. 

As  to  the  general  temperature,  this  sense  is  relative  and  is 
much  modified  by  habit,  for  what  is  cold  to  an.  inhabitant  of 
the  torrid  zone  would  be  warm  to  one  accustomed  to  a  very 
cold  climate. 

Pain  is  an  excessive  stimulation  of  the  sensory  nerves,  and 
in  it  all  finer  sensations  are  lost.  Thus,  when  a  piece  of  hot 
iron  burns  the  hand,  the  sensation  is  the  same  as  when  the 
iron  is  very  cold,  and  extreme  cold  feels  like  intense  heat. 

317.  The  Organ  of  Taste.  The  sense  of  taste  is  located 
chiefly  in  the  tongue,  but  may  also  be  referred  even  to  the 
regions  of  the  fauces.  Taste,  like  touch,  consists  in  a  particular 
mode  of  nerve  termination. 

The  tongue  is  a  muscular  organ  covered  with  mucous  mem- 
brane, and  is  richly  supplied  with  blood-vessels  and  nerves.  By 
its  complicated  movements  it  is  an  important  factor  in  chewing, 
in  swallowing,  and  in  articulate  speech.  The  surface  of  the 
tongue  is  covered  with  irregular  projections,  called  papillae,  — 
fine  hair-like  processes,  about  TT^  of  an  inch  high.  Interspersed 
with  these  are  the  fungiform  papillae.  These  are  shaped  some- 
thing like  a  mushroom,  and  may  often  be  detected  by  their 
bright  red  points  when  the  rest  of  the  tongue  is  coated. 

Towards  the  root  of  the  tongue  is  another  kind  of  papillae, 
the  circumvallate,  eight  to  fifteen  in  number,  arranged  in  the 
form  of  the  letter  V,  with  the  apex  directed  backwards.  These 
are  so  called  because  they  consist  of  a  fungiform  papilla  sur- 
rounded by  a  fold  of  mucous  membrane,  presenting  the  appear- 
ance of  being  walled  around. 

In  many  of  the  fungiform  and  most  of  the  circumvallate 
papillae  are  peculiar  structures  called  taste  buds  or  taste 


PRACTICAL    PHYSIOLOGY. 


goblets.     These  exist  in  great  numbers,  and  are  believed  to 
be  connected  with  nerve  fibers.     These  taste  buds  are  readily 

excited  by  savory 
substances,  and 
transmit  the  im- 
pression along  the 
connected  nerve. 
VKn»^m  The  tongue  is 
supplied  with  sen- 
sory fibers  by 
branches  from  the 
fifth  and  eighth 
pairs  of  cranial 
nerves.  The  for- 
mer confers  taste 
on  the  front  part 
of  the  tongue,  and 
the  latter  on  the 
back  part.  Branch- 
es of  the  latter 
also  pass  to  the  soft 
palate  and  neigh- 
boring .parts  and 
confer  taste  on 
them.  The  motor 
nerve  of  the  tongue 
is  the  ninth  pair, 
the  hypoglossal. 


FIG.  125.  — The  Tongue. 

A,  epiglottis;  B,  glands  at  the  base  of  tongue;  C,  tonsil;  D, 
median  circumvallate  papilla  ;  E,  circumvallate  papillae  ; 
F,  filiform  papillae;  H,  furrows  on  border  of  the  tongue; 
K,  fungiform  papillae. 


318.  The  Sense  of  Taste.  The  sense  of  taste  is  excited 
by  stimulation  of  the  mucous  membrane  of  the  tongue  and  of 
the  palate,  affecting  the  ends  of  the  nerve  fibers.  Taste  is 
most  acute  in  or  near  the  circumvallate  papillae.  The  middle 
of  the  tongue  is  scarcely  sensitive  to  taste,  while  the  edges  and 
the  tip  are,  as  a  rule,  highly  sensitive. 


THE    SPECIAL    SENSES.  315 

Certain  conditions  are  necessary  that  the  sense  of  taste  may 
be  exercised.  First,  the  substance  to  be  tasted  must  be  in 
solution,  or  be  soluble  in  the  fluids  of  the  mouth.  Insoluble 
substances  are  tasteless.  If  we  touch  our  tongue  to  a  piece  of 
rock  crystal,  there  is  a  sensation  of  contact  or  cold,  but  no 
sense  of  taste.  On  the  other  hand,  when  we  bring  the  tongue 
in  contact  with  a  piece  of  rock  salt,  we  experience  the  sensa- 
tions of  contact,  coolness,  and  saline  taste. 

Again,  the  mucous  membrane  of  the  mouth  must  be  moist. 
When  the  mouth  is  dry,  and  receives  substances  not  already 
in  solution,  there  is  no  saliva  ready  to  dissolve  them  ;  hence, 
they  are  tasteless.  This  absence  of  taste  is  common  with 
the  parched  mouth  during  a  fever. 

The  tongue  assists  in  bringing  the  food  in  contact  with  the 
nerves,  by  pressing  it  against  the  roof  of  the  mouth  and  the 
soft  palate,  and  thus  is  produced  the  fullest  sense  of  taste. 

319.  Physiological  Conditions  of  Taste.  The  tongue  is 
the  seat  of  sensations  which  are  quite  unlike  each  other. 
Thus,  besides  the  sense  of  taste,  there  is  the  sensation  of 
touch,  pressure,  heat  and  cold,  burning  or  acrid  feelings,  and 
those  produced  by  the  application  of  the  tongue  to  an  inter- 
rupted electric  current.  These  are  distinct  sensations,  due 
to  some  chemical  action  excited  probably  in  the  touch  cells, 
although  the  true  tastes  may  be  excited  by  causes  not  strictly 
chemical.  Thus  a  smart  tap  on  the  tongue  may  excite  the 
sensation  of  taste. 

In  the  majority  of  persons  the  back  of  the  tongue  is  most 
sensitive  to  bitters,  and  the  tip  to  sweets.  Saline  matters  are 
perceived  most  distinctly  at  the  tip,  and  acid  substances  at  the 
sides.  The  nerves  of  taste  are  sensitive  in  an  extraordinary 
degree  to  some  articles  of  food  and  certain  drugs.  For  exam- 
ple, the  taste  of  the  various  preparations  of  quinine,  pepper- 
mint, and  wild  cherry  is  got  rid  of  with  difficulty. 


3l6  PRACTICAL    PHYSIOLOGY. 

Like  the  other  special  senses,  that  of  taste  may  become 
fatigued.  The  repeated  tasting  of  one  substance  rapidly  dead- 
ens the  sensibility,  probably  by  over-stimulation.  Some  savors 
so  impress  the  nerves  of  taste  that  others  fail  to  make  any 
impression.  This  principle  is  used  to  make  disagreeable  medi- 
cine somewhat  tasteless.  Thus  a  few  cloves,  or  grains  of  coffee, 
or  a  bit  of  pepper,  eaten  before  a  dose  of  castor  oil,  renders  it 
less  nauseous. 

Flavor  is  something  more  than  taste.  It  is  in  reality  a  mixed 
sensation,  in  which  smell  and  taste  are  both  concerned,  as  is 
shown  by  the  common  observation  that  one  suffering  from  a 
cold  in  the  head,  which  blunts  his  sense  of  smell,  loses  the 
proper  flavor  of  his  food.  So  if  a  person  be  blindfolded,  and 
the  nose  pinched,  he  will  be  unable  to  distinguish  between  an 
apple  and  an  onion,  if  one  be  rubbed  on  the  tongue  after  the 
other.  As  soon  as  the  nostrils  are  opened  the  difference  is  at 
once  perceived. 

Experiment  142.  Put  a  drop  of  vinegar  on  a  friend's  tongue,  or  on 
your  own.  Notice  how  the  papillae  of  the  tongue  start  up. 

Experiment  143.  Rub  different  parts  of  the  tongue  with  the  pointed 
end  of  a  piece  of  salt  or  gum-aloes,  to  show  that  the  back  of  the  tongue  is 
most  sensitive  to  salt  and  bitter  substances. 

Experiment  144.  Repeat  the  same  with  some  sweet  or  sour  substances, 
to  show  that  the  edges  of  the  tongue  are  the  most  sensitive  to  these  sub- 
stances. 

Experiment  145.  We  often  fail  to  distinguish  between  the  sense  of 
taste  and  that  of  smell.  Chew  some  pure,  roasted  coffee,  and  it  seems  to 
have  a  distinct  taste.  "Pinch  the  nose  hard,  and  there  is  little  taste.  Coffee 
has  a  powerful  odor,  but  only  a  feeble  taste.  The  same  is  true  of  garlic, 
onions,  and  various  spices. 

Experiment  146.  Light  helps  the  sense  of  taste.  Shut  the  eyes,  and 
palatable  foods  taste  insipid.  Pinch  the  nose,  close  the  eyes,  and  see  how 
palatable  one  half  of  a  teaspoonful  of  cod-liver  oil  becomes. 

Experiment  147.  Close  the  nostrils,  shut  the  eyes,  and  attempt  to  dis- 
tinguish by  taste  alone  between  a  slice  of  an  apple  and  one  of  a  potato. 


THE    SPECIAL    SENSES.  317 

320.  Modifications  of  the  Sense  of  Taste.     Taste  is  modi- 
fied to  a  great  extent  by  habit,  education,  and  other  circumstances. 
Articles  of  food  that  are  unpleasant  in  early  life  often  become 
agreeable  in  later  years.    There  is  occasionally  a  craving,  espe- 
cially with  people  of  a  peculiar  nervous  organization,  for  certain 
unnatural  articles  (as  chalk  and  laundry  starch)  which  are  eaten 
without  the  least  repugnance.    Again,  the  most  savory  dishes  may 
excite  disgust,  while  the  simplest  articles  may  have  a  delicious 
flavor  to  one  long  deprived  of  them.     The  taste  for  certain 
articles  is  certainly  acquired.     This  is  often  true  of  raw  toma- 
toes, olives,  and  especially  of  tobacco. 

The  organs  of  taste  and  smell  may  be  regarded  as  necessary 
accessories  of  the  general  apparatus  of  nutrition,  and  are, 
therefore,  more  or  less  essential  to  the  maintenance  of  animal 
life.  While  taste  and  smell  are  generally  maintained  until  the 
close  of  life,  sight  and  hearing  are  often  impaired  by  time,  and 
may  be  altogether  destroyed,  the  other  vital  functions  remaining 
unimpaired. 

321.  Effect  of  Tobacco  and  Alcohol  upon  Taste.     It  would 
be  remarkable  if  tobacco  should  fail  to  injure  the  sense  of 
taste.     The  effect  produced  upon  the   tender  papillae  of  the 
tongue   by  the   nicotine-loaded   juices    and  the    acrid   smoke 
tends  to  impair  the  delicate  sensibility  of  the  entire  surface. 
The  keen  appreciation  of  fine  flavors  is  destroyed.     The  once 
clear  and  enjoyable  tastes  of  simple  objects  become  dull  and 
vapid  ;  thus  highly  spiced  and  seasoned  articles  of  food  are  in 
demand,  and  then  follows  continued  indigestion,  with  all  its 
suffering. 

Again,  the  burning,  almost  caustic  effect  of  the  stronger 
alcoholic  drinks,  and  the  acrid  pungency  of  tobacco  smoke,  are 
disastrous  to  the  finer  perceptions  of  both  taste  and  odors. 

322.  Smell.     The  sense  of  smell  is  lodged  in  the  delicate 
membrane  which   lines   the  nasal  cavities.     The  floor,   sides, 


PRACTICAL    PHYSIOLOGY. 


I    J 


and  roof  of  these  cavities  are  formed  by  certain  bones  of  the 
cranium  and  the  face.  Man,  in  common  with  all  air-breathing 
animals,  has  two  nasal  cavities.  They  communicate  with  the 
outer  air  by  two  nostrils  opening  in  front,  while  two  other 
passages  open  into  the  pharynx  behind. 

To  increase  the  area  of  the  air  passages,  the  two  light, 
spongy  turbinated  bones,  one  on  each  side,  form  narrow,  wind- 
ing channels.  The  mucous 
membrane,  with  the  branches 
of  the  olfactory  nerve,  lines 
the  dividing  wall  and  the 
inner  surfaces  of  these  wind- 
ing passages.  Below  all  these 
bones  the  lower  turbinated 
bones  may  be  said  to  divide 
the  olfactory  chamber  above 
from  the  ordinary  air 
passages. 

The  nerves  which  supply 
the  nasal  mucous  membrane 
are  derived  from  the  branch- 

riG.  120.  —  Distribution  of  Nerves  over  the 

Interior  of  the  Nostrils.     (Outer  wall.)  es  of    the   fifth  and  the  first 

A,  branches  of  the  nerves  of  smell  -  olfactory  Pair     of     Cranial     nerVCS,  - 

nerve,  or  ganglion  ;  B,  nerves  of  common  sen-  the     Olf  actory.        The     latter 

sation  to  the  nostril ;    E,  F,  G,  nerves  to  the 

palate   springing  from  a  ganglion  at  C ;    H,  however,    are    the    nerVCS    of 

vidian  nerve,  from  which  branches  D,  I,  and  J  smell  proper,  and  are  Spread 

spring  to  be  distributed  to  the  nostrils. 

out  in  a  kind  of  thick  brush 

of  minute  nerve  filaments.  It  is  in  the  mucous  membrane  of 
the  uppermost  part  of  the  cavity  of  the  nostril  that  the  nerve 
endings  of  smell  proper  reside.  The  other  nerves  which  supply 
the  nostrils  are  those  of  common  sensation  (sec.  271). 

323.   The  Sense  of  Smell.     The  sense  of  smell  is  excited 
by  the  contact  of  odorous  particles  contained  in  the  air,  with  the 


THE    SPECIAL    SENSES.  319 

fibers  of  the  olfactory  nerves,  which  are  distributed  over  the 
delicate  surface  of  the  upper  parts  of  the  nasal  cavities.  In 
the  lower  parts  are  the  endings  of  nerves  of  ordinary  sensa- 
tion. These  latter  nerves  may  be  irritated  by  some  substance 
like  ammonia,  resulting  in  a  powerfully  pungent  sensation. 
This  is  not  a  true  sensation  of  smell,  but  merely  an  irritation 
of  a  nerve  of  general  sensation. 

In  ordinary  quiet  breathing,  the  air  simply  flows  along  the 
lower  nasal  passages  into  the  pharynx,  scarcely  entering  the 
olfactory  chamber  at  all.  This  is  the  reason  why,  when  we 
wish  to  perceive  a  faint  odor,  we  sniff  up  the  air  sharply.  By 
so  doing,  the  air  which  is  forcibly  drawn  into  the  nostrils  passes 
up  even  into  the  higher  olfactory  chamber,  where  some  of  the 
floating  particles  of  the  odorous  material  come  into  contact 
with  the  nerves  of  smell. 

One  of  the  most  essential  conditions  of  the  sense  of  smell  is 
that  the  nasal  passages  be  kept  well  bathed  in  the  fluid  secreted 
by  the  lining  membrane.  At  the  beginning  of  a  cold  in  the  head, 
this  membrane  becomes  dry  and  swollen,  thus  preventing  the  en- 
trance of  air  into  the  upper  chamber,  deadening  the  sensibility 
of  the  nerves,  and  thus  the  sense  of  smell  is  greatly  diminished. 

The  delicacy  of  the  sense  of  smell  varies  greatly  in  different 
individuals  and  in  different  animals.  It  is  generally  more  acute 
in  savage  races.  It  is  highly  developed  in  both  the  carnivora 
and  the  herbivora.  Many  animals  are  more  highly  endowed 
with  this  sense  than  is  man.  The  dog,  for  example,  appears 
to  depend  on  the  sense  of  smell  almost  as  much  as  on  sight. 
It  is  well  known,  also,  that  fishes  have  a  sense  of  smell.  Frag- 
ments of  bait  thrown  into  the  water  soon  attract  them  to  a 
fishing  ground,  and  at  depths  which  little  or  no  light  can  pene- 
trate. Deer,  wild  horses,  and  antelopes  probably  surpass  all 
other  animals  in  having  a  vivid  sense  of  smell. 

Smell  has  been  defined  as  "  taste  at  a  distance,"  and  it  is 
obvious  that  these  two  senses  not  only  form  a  natural  group, 


32O  PRACTICAL    PHYSIOLOGY. 

but  are  clearly  associated  in  their  physical  action,  especially  in 
connection  with  the  perception  of  the  flavor  of  food.  The 
sense  of  odor  gives  us  information  as  to  the  quality  of  food 
and  drink,  and  more  especially  as  to  the  quality  of  the  air  we 
breathe.  Taste  is  at  the  gateway  of  the  alimentary  canal,  while 
smell  acts  as  the  sentinel  of  the  respiratory  tract.  Just  as 
taste  and  flavor  influence  nutrition  by  affecting  the  digestive 
process,  so  the  agreeable  odors  about  us,  even  those  of  the 
perfumes,  play  an  important  part  in  the  economy  of  life. 

324.  The  Sense  of  Sight.  The  sight  is  well  regarded  as 
the  highest  and  the  most  perfect  of  all  our  senses.  It  plays 
so  common  and  so  beneficent  a  part  in  the  animal  economy 
that  we  scarcely  appreciate  this  marvelous  gift.  Sight  is 
essential  not  only  to  the  simplest  matters  of  daily  comfort  and 
necessity,  but  is  also  of  prime  importance  in  the  culture  of 
the  mind  and  in  the  higher  forms  of  pleasure.  It  opens  to  us 
the  widest  and  the  most  varied  range  of  observation  and  enjoy- 
ment. The  pleasures  and  advantages  it  affords,  directly  and 
indirectly,  have  neither  cessation  nor  bounds. 

Apart  from  its  uses,  the  eye  itself  is  an  interesting  and  in- 
structive object  of  study.  It  presents  beyond  comparison  the 
most  beautiful  example  of  design  and  artistic  workmanship  to 
be  found  in  the  bodily  structure.  It  is  the  watchful  sentinel 
and  investigator  of  the  external  world.  Unlike  the  senses  of 
taste  and  smell  we  seem,  by  the  sense  of  vision,  to  become 

NOTE.  "  The  higher  intelligence  of  man  is  intimately  associated  with  the  per- 
fection of  the  eye.  Crystalline  in  its  transparency,  sensitive  in  receptivity,  delicate 
in  its  adjustments,  quick  in  its  motions,  the  eye  is  a  fitting  servant  for  the  eager 
soul,  and,  at  times,  the  truest  interpreter  between  man  and  man  of  the  spirit's 
inmost  workings.  The  rainbow's  vivid  hues  and  the  pallor  of  the  lily,  the  fair  crea- 
tions of  art  and  the  glance  of  mutual  affection,  all  are  pictured  in  its  translucent 
depths,  and  transformed  and  glorified  by  the  mind  within.  Banish  vision,  and  the 
material  universe  shrinks  for  us  to  that  which  we  may  touch  ;  sight  alone  sets  us 
free  to  pierce  the  limitless  abyss  of  space."  —  M'KENDRICK  and  SNODGRASS'S 
Physiology  of  the  Senses. 


THE    SPECIAL    SENSES.  321 

aware  of  the  existence  of  objects  which  are  entirely  apart  from 
us,  and  which  have  no  direct  or  material  link  connecting  them 
with  our  bodies.  And  yet  we  are  told  that  in  vision  the  eye  is 
affected  by  something  which  is  as  material  as  any  substance  we 
taste  or  smell. 

Physicists  tell  us  that  this  material,  known  as  the  luminifer- 
ous  ether,  permeates  the  universe,  and  by  its  vibrations  trans- 
mits movements  which  affect  the  eye,  giving  rise  to  -the 
sensation  of  light,  and  the  perception  of  even  the  most  distant 
objects.  Our  eyes  are  so  constructed  as  to  respond  to  the 
vibrations  of  this  medium  for  the  transmission  of  light. 

325.  The  Eye.  The  eye,  the  outer  instrument  of  vision,  is 
a  most  beautiful  and  ingenious  machine.  All  its  parts  are 
arranged  with  such  a  delicate  adjustment  to  one  another,  and 
such  an  exquisite  adaptation  of  every  part  to  the  great  object 
of  the  whole,  that  the  eye  is  properly  regarded  as  one  of  the 
wonders  of  nature. 

The  eyeball  is  nearly  spherical  in  shape,  but  is  slightly 
elongated  from  before  backwards.  The  front  part  is  clear  and 
transparent,  and  bulges  somewhat  prominently  to  allow  the 
entrance  of  the  rays  of  light.  The  eye  rests  in  a  bowl-shaped 
socket,  called  the  orbit,  formed  by  parts  of  various  bones  of 
the  head  and  face.  The  margins  of  this  cavity  are  formed  of 
strong  bone  which  can  withstand  heavy  blows.  The  socket  is 
padded  with  loose,  fatty  tissue,  and  certain  membranes,  which 
serve  as  a  soft  and  yielding  bed  in  which  the  eyeball  can  rest 
and  move  without  injury.  In  a  severe  sickness  this  fatty  tissue 
is  absorbed,  and  this  fact  explains  the  sunken  appearance  of 
the  eyes. 

The  orbit  is  pierced  through  its  posterior  surface  by  an 
opening  through  which  the  nerve  of  sight,  the  optic,  passes  to 
the  eyeball.  We  may  think  of  the  optic  nerve  holding  the 
eyeball  much  as  the  stem  holds  the  apple.  It  is  the  function  of 


322 


PRACTICAL    PHYSIOLOGY. 


this  most  important  nerve  to  transmit  retinal  impressions  to  the 
seat  of  consciousness  in  the  brain,  where  they  are  interpreted. 

The  eye  is  bathed  with  a  watery  fluid,  and  protected  by  the 
eyelids  and  the  eyebrows  ;  it  is  moved  in  various  directions, 
by  muscles,  all  of  which  will  soon  be  described. 


••- SUPER  (OR  REGTUS 


-CILIARY  PROCESSES 
•-SUSPENSORY  LIGAMENT 


--SUSPENSORY  LIGAMENT 
CILIARY  PROCESSES 


CHOROID 


OPTIC  NERVE 


CHOROID 


-INFERIOR  RECTHS 
FIG.  127.  —  Section  of  the  Human  Eye. 

326.  The  Coats  of  the  Eyeball.  The  eyeball  proper  is 
elastic  but  firm,  and  is  composed  of  three  coats,  or  layers,  each 
of  which  performs  important  functions.  These  coats  are  the 
sclerotic,  the  choroid,  and  the  retina. 

The  sclerotic  coat  is  the  outside  layer  and  enclosing  mem- 
brane of  the  eyeball.  It  is  a  tough,  fibrous  coat  for  the  pro- 
tection and  maintenance  of  the  shape  of  the  eye.  It  is  white 


THE    SPECIAL    SENSES.  323 

and  glistening  in  appearance,  and  is  in  part  visible,  to  which 
the  phrase,  "  the  white  of  the  eye,"  is  applied.  To  this  coat, 
which  serves  as  a  kind  of  framework  for  the  eye,  are  attached 
the  muscles  which  move  the  eyeball.  In  front  of  the  globe, 
the  sclerotic  passes  into  a  transparent  circular  portion  forming 
a  window  through  which  one  can  see  into  the  interior.  This  is 
the  cornea. 

The  cornea,  a  clear,  transparent,  circular  disk,  fits  into  the 
sclerotic,  somewhat  as  the  crystal  fits  into  the  metallic  case  of 
a  watch,  forming  a  covering  for  its  dial.  It  projects  from  the 
general  contour  of  the  eyeball,  not  unlike  a  rounded  bay- 
window,  and  is  often  spoken  of  as  the  "  window  of  the  eye." 

Lining  the  inner  surface  of  the  sclerotic  is  the  second  coat, 
the  choroid.  It  is  dark  in  color  and  fragile  in  structure,  and 
is  made  up  almost  entirely  of  blood-vessels  and  nerves.  As 
the  choroid  approaches  the  front  part  of  the  eyeball,  its  parts 
become  folded  upon  themselves  into  a  series  of  ridges,  called 
ciliary  processes.  These  folds  gradually  become  larger,  and 
at  last  merge  into  the  ciliary  or  accommodation  muscle  of  the 
eye.  The  circular  space  thus  left  in  front  by  the  termination 
of  the  choroid  is  occupied  by  the  iris,  a  thin,  circular  curtain, 
suspended  in  the  aqueous  humor  behind  the  cornea  and  in 
front  of  the  crystalline  lens.  In  its  center  is  a  round  opening 
for  the  admission  of  light. 

This  is  the  pupil,  which  appears  as  if  it  were  a  black  spot. 
The  back  of  the  iris  is  lined  with  dark  pigment,  and  as  the 
coloring  matter  is  more  or  less  abundant,  we  may  have  a 
variety  of  colors.  This  pigment  layer  and  that  of  the  choroid 
and  retina  absorb  the  light  entering  the  eye,  so  that  little  is 
reflected. 

The  pupil  appears  black,  just  as  the  open  doorway  to  a  dark 
closet  seems  black.  The  margin  of  the  iris  is  firmly  connected 
with  the  eyeball  all  round,  at  the  junction  of  the  sclerotic  and 
the  cornea. 


324  PRACTICAL    PHYSIOLOGY. 

327.  The  Retina.  The  third  and  innermost  coat  of  the 
eyeball  is  the  retina.  This  is  the  perceptive  coat,  without 
which  it  would  be  impossible  to  see,  and  upon  which  the 
images  of  external  objects  are  received.  It  lines  nearly  the 
whole  of  the  inner  surface  of  the  posterior  chamber,  resting  on 
the  inner  surface  of  the  choroid.  It  is  with  the  retina,  there- 
fore, that  the  vitreous  humor  is  in  contact. 

The  retina  is  a  very  thin,  delicate  membrane.  Although 
very  thin,  it  is  made  up  of  ten  distinct  layers,  and  is  so  com- 
plicated in  structure  that  not  even  a  general  description  will  be 
attempted  in  this  book.  It  does  not  extend  quite  to  the  front 
limits  of  the  posterior  chamber,  but  stops  short  in  a  scalloped 
border,  a  little  behind  the  ciliary  processes.  This  is  the  nerve 
coat  of  the  eye,  and  forms  the  terminal  organ  of  vision.  It  is 
really  an  expansion  of  the  ultimate  fibers  of  the  optic  nerve, 
by  means  of  which  impressions  are  sent  to  the  brain. 

The  retina  contains  curious  structures  which  can  be  seen 
only  with  the  aid  of  the  microscope.  For  instance,  a  layer 
near  the  choroid  is  made  up  of  nerve  cells  arranged  in  innum- 
erable cylinders  called  "  rods  and  cones,"  and  packed  together 
not  unlike  the  seeds  of  a  sunflower.  These  rods  and  cones 
are  to  be  regarded  as  the  peculiar  modes  of  termination  of  the 

Experiment  148.  Close  one  eye  and  look  steadily  at  the  small  a  in 
the  figure  below.  The  other  letters  will  also  be  -visible  at  the  same 
time.  If  now  the  page  be  brought  slowly  nearer  to  the  eye  while  the  eye 
is  kept  steadily  looking  at  the  small  a,  the  large  A  will  disappear  at  a  cer- 
tain point,  reappearing  when  the  book  is  brought  still  nearer. 

a  o  Ax 


On  the  reappearance  of  the  A  it  will  be  noted  that  it  comes  into  view  from 
the  inner  side,  the  x  being  seen  before  it.  If  now  wre  move  the  book  back 
towards  its  original  place,  the  A  will  again  disappear,  coming  again  into 
view  from  the  outer  side  when  the  o  is  seen  before  it. 


THE    SPECIAL    SENSES.  32$ 

nerve  filaments  of  the  eye,  just  as  the  taste  buds  are  the  modes 
of  termination  of  the  nerve  of  taste  in  the  tongue,  and  just  as  the 
touch  corpuscles  are  the  terminations  of  the  nerves  in  the  skin. 

328.  Inner  Structure  of  the  Eye.  Let  us  imagine  an  eye- 
ball divided  through  the  middle  from  above  downwards.  Let 
us  now  start  in  front  and  observe  its  parts  (Fig.  127).  We 


OBJECT 


EYE 


FIG.  128. —  Diagram  illustrating  the  Manner  in  which  the  Image  of  an 
Object  is  brought  to  a  Focus  on  the  Retina. 

come  first  to  the  cornea,  which  has  just  been  described.  The 
iris  forms  a  sort  of  vertical  partition,  dividing  the  cavity  of  the 
eyeball  into  two  chambers. 

The  anterior  chamber  occupies  the  space  between  the  cornea 
and  the  iris,  and  is  filled  with  a  thin,  watery  fluid  called  the 
aqueous  humor. 

The  portion  behind  the  iris  forms  the  posterior  chamber, 
and  contains  the  crystalline  lens  and  a  transparent,  jelly-like 
fluid,  the  vitreous  humor.  This  fluid  is  never  renewed,  and 
its  loss  is  popularly  described  by  the  phrase,  '  when  the  eye 
runs  out." 

Experiment  149.  The  retina  is  not  sensitive  where  the  optic  nerve 
enters  the  eyeball.  This  is  called  the  "  blind  spot."  Put  two  ink-bottles 
about  two  feet  apart,  on  a  table  covered  with  white  paper.  Close  the 
left  eye,  and  fix  the  right  steadily  on  the  left-hand  inkstand,  gradually 
varying  the  distance  from  the  eye  to  the  ink-bottle.  At  a  certain  distance 
the  right-hand  bottle  will  disappear;  but  nearer  or  farther  than  that,  it 
will  be  plainly  seen. 


326 


PRACTICAL    PHYSIOLOGY. 


The  vitreous  humor  fills  about  four-fifths  of  the  eyeball  and 
prevents  it  from  falling  into  a  shapeless  mass.  It  also  serves 
to  hold  the  choroid  and  the  retina  in  position,  and  to  maintain 
the  proper  relations  of  the  inner  structures  of  the  eye. 

The  iris  consists  of  a  framework  of  connective  tissue,  the 
surface  of  which  is  lined  by  cells  containing  pigment,  which 
gives  color  to  the  eye. 

Bundles  of  involuntary  muscular  fibers  are  found  in  the  sub- 
stance of  the  iris.  Some  are  arranged  in  a  ring  round  the 
margin  of  the  pupil  ;  others  radiate  from  it  like  the  spokes  of 
a  wheel.  When  the  circular  fibers  contract,  the  pupil  is  made 
smaller,  but  if  these  fibers  relax,  the  radiating  fibers  cause  the 
pupil  to  dilate  more  or  less  widely. 

329.  The  Crystalline  Lens.  Just  behind  the  pupil  and 
close  to  the  iris  is  a  semi-solid,  double-convex  body,  called  the 
crystalline  lens.  It  is  shaped  like  a  magnifying  glass,  convex 


FIG.  129. —  Diagram  showing  the  Change  in  the  Lens  during  Accommodation. 

On  the  right  the  lens  is  arranged  for  distant  vision,  the  ciliary  muscle  is  relaxed  and  the 
ligament  D  is  tense,  so  flattening  by  its  compression  the  front  of  the  lens  C;  on  the 
left  the  muscle  A  is  acting,  and  this  relaxes  the  ligament  and  allows  the  lens  B  to 
become  more  convex,  and  so  fitted  for  the  vision  of  near  objects. 

on  each  side,  but  with  the  posterior  surface  more  convex  than 
the  anterior.  In  health  it  is  perfectly  clear  and  transparent, 
and  highly  elastic.  When  the  lens  becomes  opaque,  from 
change  in  old  age,  or  from  ulcers  or  wounds,  we  have  the  dis- 
ease known  as  cataract. 


THE    SPECIAL    SENSES. 

The  lens  is  not  placed  loosely  in  the  eyeball,  but  is  enclosed 
in  a  transparent  and  elastic  capsule  suspended  throughout  its 
circumference  by  a  ligament  called  the  suspensory  ligament. 
This  ligament  not  only  retains  the  lens  in  place,  but  is  capable 
of  altering  its  shape.  In  ordinary  conditions  of  the  eye,  this 
ligament  is  kept  tense  so  that  the  front  part  of  the  lens  is 
flattened  somewhat  by  the  pressure  on  it. 

All  around  the  edge,  where  the  cornea,  sclerotic,  and  choroid 
meet,  is  a  ring  of  involuntary  muscular  fibers,  forming  the 
ciliary  muscle.  When  these  fibers  contract,  they  draw  for- 
wards the  attachment  of  the  suspensory  ligament  of  the  lens, 
the  pressure  of  which  on  the  lens  is  consequently  diminished. 
The  elasticity  of  the  lens  causes  it  at  once  to  bulge  forwards, 
and  it  becomes  more  convex. 

The  ciliary  muscle  is  thus  known  as  the  muscle  of  accom- 
modation, because  it  has  the  power  to  accommodate  the  eye 
to  near  and  distant  objects.  In  this  respect  it  corresponds 
in  its  use  to  the  adjusting  screw  in  the  opera-glass  and  the 
microscope. 

330.   The  Eye  Compared  to  the  Photographic  Camera.     As  an 

optical  instrument,  the  eye  may  be  aptly  compared,  in  many  particu- 
lars, to  the  photographic  camera.  The  latter,  of  course,  is  much 
simpler  in  structure.  The  eyelid  forms  the  cap,  which  being  re- 
moved, the  light  from  the  object  streams  through  the  eye  and  passes 
across  the  dark  chamber  to  the  retina  behind,  which  corresponds  to 
the  sensitive  plate  of  the  camera.  The  transparent  structures  through 
which  the  rays  of  light  pass  represent  the  lenses.  To  prevent  any 
reflected  light  from  striking  the  plate  and  interfering  with  the  sharp- 
ness of  the  picture,  the  interior  of  the  photographic  camera  box  is 
darkened.  The  pigmented  layer  of  the  choroid  coat  represents  this 
blackened  lining. 

In  the  camera,  the  artist  uses  a  thumb-screw  to  bring  to  a  focus 
on  the  sensitive  plate  the  rays  of  light  coming  from  objects  at  differ- 
ent distances.  Thus  the  lens  of  the  camera  may  be  moved  nearer  to 
or  farther  from  the  object.  In  order  to  obtain  clear  images,  the 


328  PRACTICAL    PHYSIOLOGY. 

same  result  must  be  accomplished  by  the  eye.  When  the  eye  is 
focused  for  near  objects,  those  at  a  distance  are  blurred,  and  when 
focused  for  distant  objects,  those  near  at  hand  are  indistinct.  Now, 
in  the  eye  there  is  no  arrangement  to  alter  the  position  of  the  lenses, 
as  in  the  camera,  but  the  same  result  is  obtained  by  what  is  called 
"  accommodation." 

Again,  every  camera  has  an  arrangement  of  diaphragms  regulating 
the  amount  of  light.  This  is  a  rude  contrivance  compared  with  the 
iris,  which  by  means  of  its  muscular  fibers  can  in  a  moment  alter  the 
size  of  the  pupil,  thus  serving  a  similar  purpose. 


OBJECT 


PHOTOGRAPHIC  CAMERA 


FIG.  130.  —  Illustrating  the  manner  in  which  the  Image  of  an  Object  is 
brought  to  a  Focus  in  a  Photographer's  Camera. 

331.   The  Refractive  Media  of  the  Eye.     The  eye  is  a 

closed  chamber  into  which  no  light  can  pass  but  through  the 
cornea.  All  the  rays  that  enter  the  eye  must  also  pass  through 
the  crystalline  lens,  which  brings  them  to  a  focus,  as  any  ordi- 
nary lens  would  do. 

Now,  if  the  media  through  which  the  light  from  an  object 
passes  to  reach  the  retina  were  all  of  the  same  density  as  the 
air,  and  were  also  plane  surfaces,  an  impression  would  be  pro- 
duced, but  the  image  would  not  be  distinct.  The  action  of 
the  lens  is  aided  by  several  refractive  media  in  the  eye. 
These  media  are  the  cornea,  the  aqueous  humor,  and  the  vitre- 
ous humor.  By  reason  of  their  shape  and  density  these  media 
refract  the  rays  of  light,  and  bring  them  to  a  focus  upon  the 
retina,  thus  aiding  in  producing  a  sharp  and  distinct  image  of 
the  object.  Each  point  of  the  image  being  the  focus  or  meet 


THE  SPECIAL  SENSES.  329 

ing-place  of  a  vast  number  of  rays  coming  from  the  correspond- 
ing point  of  the  object  is  sufficiently  bright  to  stimulate  the 
retina  to  action.1 

Thus,  the  moment  rays  of  light  enter  the  eye  they  are  bent 
out  of  their  course.  By  the  action  of  the  crystalline  lens, 
aided  by  the  refractive  media,  the  rays  of  light  that  are  parallel 
when  they  fall  upon  the  normal  eye  are  brought  to  a  focus  on 
the  retina. 

If  the  entire  optical  apparatus  of  the  eye  were  rigid  and 
immovable,  one  of  three  things  would  be  necessary,  in  order  to 
obtain  a  clear  image  of  an  object ;  for  only  parallel  rays  (that 
is,  rays  coming  from  objects  distant  about  thirty  feet  or  more), 
are  brought  to  a  focus  in  the 
average  normal  eye,  unless 
some  change  is  brought  about 
in  the  refractive  media.  First,  FIG.  131.  —  The  Actual  Size  of  the  Test- 
the  posterior  wall  of  the  eye  TyPe' which  should  te  seen  by  the  Normal 

•*  Eye  at  a  Distance  of  Twenty  Feet, 

must  be  moved  further  back, 

or  the  lens  would  have  to  be  capable  of  movement,  or  there 
must  be  some  way  of  increasing  the  focusing  power  of  the 
lens.  In  the  eye  it  is  the  convexity  of  the  lens  that  is  altered  so 
that  the  eye  is  capable  of  adjusting  itself  to  different  distances.2 

332.  The  More  Common  Defects  of  Vision.  The  eye  may 
be  free  from  disease  and  perfectly  sound,  and  yet  vision  be 
indistinct,  because  the  rays  of  light  are  not  accurately  brought 

1  If  an  eye  removed  from  its  socket  be  stripped  posteriorly  of  the  sclerotic  coat, 
an  inverted  image  of  the  field  of  view  will  be  seen  on  the  retina  ;  but  if  the  lens  or 
other  part  of  the  refractive  media  be  removed,  the  image  will  become  blurred  or 
disappear  altogether. 

2  This  change  in  the  convexity  of  the  lens  is  only  a  slight  one,  as  the  difference  in 
the  focal  point  between  rays  from  an  object  twenty  feet  distant  and  one  four  inches 
distant  is  only  one-tenth  of  an  inch.     While  this  muscular  action  is  taking  place, 
the  pupil  contracts  and  the  eyeballs  converge  by  the  action  of  the  internal  rectus 
muscles.     These  three  acts  are  due  to  the  third  nerve  (the  motor  oculi).     This  is 
necessary  in  order  that  each  part  should  be  imprinted  on  the  same  portion  of  the 
retina,  otherwise  there  would  be  double  vision. 


330 


PRACTICAL    PHYSIOLOGY. 


print>    and    tired    eyeSj    the 


to  a  focus  on  the  retina.  "  Old  sight,"  known  as  presbyopia, 
is  a  common  defect  of  vision  in  advancing  years.  This  is  a 
partial  loss  of  the  power  to  accommodate  the  eye  to  different 
distances.  This  defect  is  caused  by  an  increase  in  the  density 
of  the  crystalline  lens,  and  an  accompanying  diminution  in  the 
ability  to  change  its  form.  The  far  point  of  vision  is  not 

changed,  but  the  near  point 
is  removed  so  far  from  the 
eye,  that  small  objects  are 
•p  no  longer  visible. 

Hence,    when    a   person 
about  forty-five  years  of  age 

FIG.  132.  —  Diagram  illustrating  the  Hyper-     complains  of  dim  light,  poor 
metropic  (far-sighted)  Eye. 

The  image  P'  of  a  point  P  falls  behind  the  retina 
m  the  unaccommodated  eye.  By  means  or  a 
convex  lens  it  may  be  focused  on  the  retina  advice  of  an  Optician.  A 
without  accommodation  (dotted  lines).  (To  save  conyex  lens  may  be  needed 
space  P  is  placed  much  too  near  the  eye.)  J 

to  aid  the  failing  power  to 

increase  the  convexity  of  the  lens,  and  to  assist  it  in  bringing 
the  divergent  rays  of  light  to  a  focus. 

In  "long  sight,"  or  hypermetropia,  both  the  near  and  far 
point  of  vision  are  concerned,  and  there  is  no  distinct  vision 
at  any  distance  without  a  strain.  It  is  a  defect  in  the  focus, 
dependent  upon  the  form  of  the  eyes,  and  exists  in  childhood. 
The  axis  of  the  eyeball  is  too  short,  and  the  focus  falls  beyond 
the  retina,  which  is  too  near  the  cornea.  In  childhood  this 
strain  may  pass  unnoticed,  but  sooner  or  later  it  manifests 
itself  by  a  sense  of  fatigue,  dizziness,  and  a  blurred  and  indis- 
tinct vision.  The  remedy  is  in  the  use  of  convex  glasses  to 
converge  parallel  rays  of  light  before  they  enter  the  eye.  The 
muscles  of  accommodation  are  thus  relieved  of  their  extra  work. 

"  Short  sight,"  known  as  myopia,  is  one  of  the  commonest 
defects  of  vision.  In  this  defect  the  axis  of  the  eye,  or  the 
distance  between  the  cornea  and  the  retina,  is  too  long  and 


THE    SPECIAL    SENSES.  331 

the  rays  of  light  are  brought  to  a  focus  in  front  of  the  retina. 
The  tendency  to  short-sightedness  exists  in  many  cases  at 
birth,  and  is  largely  hereditary.  It  is  alarmingly  common  with 
those  who  make  a  severe  demand  upon  the  eyes.  During 
childhood  there  is  a  marked  increase  of  near-sightedness.  The 
results  of  imprudence  and  abuse,  in  matters  of  eyesight,  are  so 
disastrous,  especially  during  school  life,  that  the  question  of 
short  sight  becomes  one  of  paramount  importance. 

Experiment  150.  With  a  hand-mirror  reflect  the  sunlight  on  a  white 
wall.  Look  steadily  at  the  spot  for  a  full  minute,  and  then  let  the  mirror 
suddenly  be  removed.  The  "  complementary  "  color  —  a  dark  spot  —  will 
appear. 

Experiment  151.  To  show  that  impressions  made  upon  the  retina  do  not 
disappear  at  once.  Look  steadily  at  a  bright  light  for  a  moment  or  two, 
and  then  turn  away  suddenly,  or  shut  the  eyes.  A  gleam  of  light  will  be 
seen  for  a  second  or  two. 

Look  steadily  at  a  well-lighted  window  for  a  few  seconds,  and  then  turn 
the  eyes  suddenly  to  a  darkened  wall.  The  window  frame  may  be  plainly 
seen  for  a  moment. 

Glance  at  the  sun  for  a  moment,  close  the  eyes  and  the  image  of  the 
sun  may  be  seen  for  a  few  seconds. 

Experiment  152.  Take  a  round  piece  of  white  cardboard  the  size  of  a 
saucer,  and  paint  it  in  alternate  rings  of  red  and  yellow,  —  two  primary 
colors.  Thrust  a  pin  through  the  center  and  rotate  it  rapidly.  The  eye 
perceives  neither  color,  but  orange,  —  the  secondary  color. 

Experiment  153.  To  note  the  shadows  cast  upon  the  retina  by  opaque 
matters  in  the  vitreous  humor  (popularly  known  as  floating  specks,  or  gos- 
samer threads),  look  through  a  small  pinhole  in  a  card  at  a  bright  light 
covered  by  a  ground-glass  shade. 

Experiment  154.  To  illustrate  accommodation.  Standing  near  a  source 
of  light,  close  one  eye,  hold  up  both  forefingers  not  quite  in  a  line,  keeping 
one  finger  about  six  or  seven  inches  from  the  other  eye,  and  the  other 
forefinger  about  sixteen  to  eighteen  inches  from  the  eye.  Look  at  the  near 
finger  ;  a  distinct  image  is  obtained  of  it,  while  the  far  one  is  blurred  or 
indistinct.  Look  at  the  far  image  ;  it  becomes  distinct,  while  the  near  one 
becomes  blurred.  Observe  that  in  accommodating  for  the  near  object, 
one  is  conscious  of  a  distinct  effort. 


332  PRACTICAL    PHYSIOLOGY. 

In  many  cases  near-sightedness  becomes  a  serious  matter 
and  demands  skillful  advice  and  careful  treatment.  To  remedy 
this  defect,  something  must  be  done  to  throw  farther  back  the 
rays  proceeding  from  an  object  so  that  they  will  come  to  a 
focus  exactly  on  the  retina.  This  is  done  by  means  of  con- 
cave glasses,  properly  adjusted  to  meet  the  conditions  of  the 

eyes.  The  selection  of  suit- 
able glasses  calls  for  great 
care,  as  much  harm  may  be 
done  by  using  glasses  not 
properly  fitted  to  the  eye. 
There  is  an  optical  con- 

FIG.  133-  Diagram  illustrating  the  Myopic      diti°n  °f  Jhe  ^  knOWn  SS 

(near-sighted)  Eye.  astigmatism,  in  which  the 

The  image  P'  of  a  distant  point  P  falls  in  front  of     COmea    is    USUally    at  fault. 

iTt.Zi^SnS:^?   I"  *is  defect  of  vision  the 

made  to  fall  on  the  retina  (dotted  lines).     (To     curvature  of    the  COmea    is 
save  space  Pis  placed  much  too  near  the  eye)      greater     in      Qne     meridian 

than  in  another.  As  a  result  the  rays  from  an  object  are  not 
all  brought  to  the  same  focus.  Objects  appear  distorted  or  are 
seen  with  unequal  clearness.  Glasses  of  a  peculiar  shape  are 
required  to  counteract  this  defect. 

333.  The  Movements  of  the  Eyes.  In  order  that  our  eyes 
may  be  efficient  instruments  of  vision,  it  is  necessary  that  they 
have  the  power  of  moving  independently  of  the  head.  The 
mechanical  arrangement  by  which  the  eyeballs  are  moved  in 
different  directions  is  quite  simple.  It  is  done  by  six  little 
muscles,  arranged  in  three  pairs,  which,  with  one  exception, 
originate  in  the  back  of  the  cavity  in  which  the  eye  rests. 
Four  of  these  muscles  run  a  straight  course  and  are  called  the 
recti.  The  remaining  two  muscles  bend  in  their  course  and  are 
called  oblique.  The  coordination  of  these  tiny  muscles  is  mar- 
vellous in  its  delicacy,  accuracy,  and  rapidity  of  action. 


THE    SPECIAL    SENSES. 


333 


When,  for  any  cause,  the  coordination  is  faulty,  "cross  eye," 
technically  called  strabismus,  is  produced.  Thus,  if  the  in- 
ternal rectus  is  shortened,  the  eye  turns  in  ;  if  the  external 
rectus,  the  eye  turns  out,  producing  what  is  known  as  "  wall  eye." 
It  is  thus  evident  that  the  beauty  of  the  internal  mechanism  of 
the  eye  has  its  fitting  complement  in  the  precision,  delicacy, 
and  range  of  movement  conferred  upon  it  by  its  muscles. 

334.  The  Eyelids  and  Eyebrows.  The  eye  is  adorned  and 
protected  by  the  eyelids,  eyelashes,  and  eyebrows. 

The  eyelids,  two  in  number,  move  over  the  front  of  the 
eyeball  and  protect  it  from  injury.  They  consist  of  folds  of 


FIG.  134. —  Muscles  of  the  Eyeball. 

A,  attachment  of  tendon  connected  with  the  three  recti  muscles ;  B,  external  rectus, 
divided  and  turned  downward,  to  expose  the  internus  rectus ;  C,  inferior  rectus ; 
D,  internal  rectus;  E,  superior  rectus;  F,  superior  oblique;  H,  pulley  and  reflected 
portion  of  the  superior  oblique;  K,  inferior  oblique;  L,  levator  palpebri  superioris; 
M,  middle  portion  of  the  same  muscle  (L);  N,  optic  nerve. 

skin  lined  with  mucous  membrane,  kept  in  shape  by  a  layer  of 
fibrous  material.  Near  the  inner  surface  of  the  lids  is  a  row 
of  twenty  or  thirty  glands,  known  as  the  Meibomian  glands, 
which  open  on  the  free  edges  of  each  lid.  When  one  of  these 


334  PRACTICAL    PHYSIOLOGY. 

glands  is  blocked  by  its  own  secretion,  the  inflammation  which 
results  is  called  a  "sty." 

The  inner  lining  membrane  of  the  eyelids  is  known  as  the 
conjunctiva  ;  it  is  richly  supplied  with  blood-vessels  and  nerves. 
After  lining  the  lids  it  is  reflected  on  to  the  eyeballs.  It  is 
this  membrane  which  is  occasionally  inflamed  from  taking 
cold. 

The  free  edges  of  the  lids  are  bordered  with  two  or  more 
rows  of  hairs  called  the  eyelashes,  which  serve  both  for  orna- 
ment and  for  use.  They  help  to  protect  the  eyes  from  dust, 
and  to  a  certain  extent  to  shade  them.  Their  loss  gives  a 
peculiar,  unsightly  look  to  the  face. 

The  upper  border  of  the  orbit  is  provided  with  a  fringe  of 
short,  stiff  hairs,  the  eyebrows.  They  help  to  shade  the  eyes 
from  excessive  light,  and  to  protect  the  eyelids  from  perspira- 
tion, which  would  otherwise  cause  serious  discomfort. 

335.  The  Lacrymal  Apparatus.  Nature  provides  a  special 
secretion,  the  tears,  to  moisten  and  protect  the  eye.  The 
apparatus  producing  this  secretion  consists  of  the  lacrymal  or 
tear  gland  and  lacrymal  canals  or  tear  passages  (Fig.  136). 

Outside  of  the  eyeball,  in  the  loose,  fatty  tissue  of  the  orbit, 
in  the  upper  and  outer  corner  is  the  lacrymal  or  tear  gland. 
It  is  about  the  size  of  a  small  almond  and  from  it  lead  several 
little  canals  which  open  on  the  inner  surface  of  the  upper  lid. 
The  fluid  from  the  gland  flows  out  by  these  openings  over  the 
eyeball,  and  is  collected  at  the  inner  or  nasal  corner.  Here  in 
each  lid  is  a  little  reddish  elevation,  or  lacrymal  caruncle,  in 
which  is  an  opening,  communicating  with  a  small  canal  in  the 
lid  which  joins  the  lacrymal  sac,  lodged  between  the  orbit  and 
the  bridge  of  the  nose  (Fig.  137). 

From  this  sac  there  passes  a  channel,  the  nasal  duct,  about 
one-half  of  an  inch  long,  leading  into  the  lower  portion  of  the 
nostril.  The  fluid  which  has  flowed  over  the  eye  is  drained 


THE    SPECIAL    SENSES. 


335 


off  by  these  canals  into  the  nose.  During  sleep  this  secretion 
is  much  diminished.  When  the  eyes  are  open  the  quantity  is 
sufficient  to  moisten  the  eyeball,  the  excess  being  carried  into 
the  nose  so  gradually  that  the  attention  is  not  attracted  to  it. 

The  lacrymal  canals  are  at  times  blocked  by  inflammation  of 
the  nasal  duct,  and  the  fluid  collects  in  the  corners  of  the  eyelids 
and  overflows  down  the  cheeks,  producing  much  inconvenience. 
The  lining  membrane  of  the  eyelids  through  these  canals  is 
continuous  with  that  of  the  nostrils.  Hence,  when  the  lining 
membrane  of  the  eye  is  red  and  swollen,  as  during  a  cold,  the 
nasal  passages  are  also  irri- 
tated, and  when  the  nasal 
membrane  is  inflamed,  the 
irritation  is  apt  to  pass  up- 
wards and  affect  the  eyelids. 

336.    The    Tears.       The 

lacrymal  or  tear  gland  is 
under  the  control  of  the 
nervous  system.  Thus,  if 
anything  irritates  the  eyelids, 
the  sensory  nerves  are  stimu- 
lated and  the  impression  is 
carried  to  the  brain.  Thence  FlG-  T35-— Lacrymal  Gland  and  Ducts. 

the   nerve   impulses   travel    tO     A,  lachrymal  gland,  the  size  of  a  small  almond, 

1  lodged  in  a  shallow  depression  in  the  bones  of 

the    lacrymal   glands,  leading        the  orbit;  B,  lachrymal  ducts  (usually  seven), 

to  an  increased  flow  of  their      which  f°rm, a  row  of  openings  into  the  con- 

junctival  fold. 

secretion.     The  irritation  of 

the  sensory  nerves  in  the  nasal  passages  by  smelling  such 
substances  as  onions,  or  pungent  salts,  often  causes  a  copious 
flow  of  tears. 

Various  mental  emotions,  as  joy  and  grief,  may  produce 
similar  results.  In  these  cases  the  glands  secrete  the  fluid  in 
such  quantities  that  it  cannot  escape  by  the  lacrymal  canals, 


PRACTICAL    PHYSIOLOGY. 

and  the  excess  rolls  over  the  cheeks  as  tears.  Excessive  grief 
sometimes  acts  on  the  nerve  centers  in  exactly  the  opposite 
manner,  so  that  the  activity  of  the  glands  is  arrested  and  less 
fluid  is  secreted.  This  explains  why  some  people  do  not  shed 
tears  in  times  of  deep  grief. 

Experiment  155.  Gently  turn  the  inner  part  of  your  lower  eyelid  down. 
Look  in  a  mirror,  and  the  small  lacrymal  point,  or  opening  into  the  nasal 
duct,  may  be  observed. 

337.  Color-blindness.     There  is  an  abnormal  condition  of 
vision  called  color-blindness,  in  which  the  power  of  discrimina- 
tion between  different  colors  is  impaired.     Experiment  shows 
that  ninety-six  out  of  every  one  hundred  men  agree  as  to  the 
identity  or  the  difference  of  color,   while  the  remaining  four 
show  a  defective  perception  of  color. 

The  first  may  be  said  to  have  normal  vision ;  the  second  are 
called  color-blind.  It  is  a  curious  fact  that  ten  times  more  men 
than  women  are  color-blind. 

In  its  true  sense,  color-blindness  is  always  congenital,  often 
hereditary.  This  condition  of  abnormal  vision  is  totally  incur- 
able. A  person  may  be  color-blind  and  not  know  it  until  the 
defect  is  accidentally  revealed.  The  common  form  of  defective 
color-vision  is  the  inability  to  distinguish  between  red  and 
green.  As  green  lights  mean  safety,  and  red  lights  danger,  on 
railroads,  on  shipboard,  and  elsewhere,  it  becomes  of  paramount 
importance  that  no  one  who  is  color-blind  should  be  employed 
in  such  service.  Various  tests  are  now  required  by  statute  law 
in  many  states  to  be  used  for  the  detection  of  such  defects  of 
vision  among  employees  in  certain  occupations. 

338.  School  Life  and  the  Eyesight.     The  eyes  of  children  need 
more  care  than  those  of  adults,  because  their  eyes  are  still  in  the 
course  of  development.     The  eyes,  like  any  other  organ  which  is  yet 
to  attain  its  full  growth,  require  more  care  in  their  use  than  one 
which  has  already  reached  its  full  size.     They  are  peculiarly  liable  to 


THE    SPECIAL    SENSES.  337 

be  affected  by  improper  or  defective  light.  Hence  the  care  of  the 
eyes  during  school  life  is  a  matter  of  the  most  practical  importance. 

In  no  matter  of  health  can  the  teacher  do  a  more  distinct  service 
than  in  looking  after  the  eyesight  of  the  pupils.  Children  suffering 
from  defective  vision  are  sometimes  punished  by  teachers  for  supposed 
stupidity.  Such  pupils,  as  well  as  the  deaf,  are  peculiarly  sensitive 
to  their  defects.  Every  schoolroom  should  have  plenty  of  light ;  it 
should  come  from  either  side  or  the  rear,  and  should  be  regulated 
with  suitable  shades  and  curtains. 

Pupils  should  not  be  allowed  to  form  the  bad  habit  of  reading  with 
the  book  held  close  to  the  eyes.  The  long  search  on  maps  for 
obscure  names  printed  in  letters  of  bad  and  trying  type  should  be 
discouraged.  Straining  the  eyes  in  trying  to  read  from  slates  and 
blackboards,  in  the  last  hour  of  the  afternoon  session,  or  in  cloudy 
weather,  may  do  a  lifelong  injury  to  the  eyesight.  Avoid  the  use,  so 
far  as  possible,  especially  in  a  defective  light,  of  text-books  which 
are  printed  on  battered  type  and  worn  plates. 

The  seat  and  desk  of  each  scholar  should  be  carefully  arranged 
to  suit  the  eyesight,  as  well  as  the  bones  and  muscles.  Special  pains 
should  be  taken  with  the  near-sighted  pupils,  and  those  who  return  to 
school  after  an  attack  of  scarlet  fever,  measles,  or  diphtheria. 

Experiment  156.  To  test  color-blindness.  On  no  account  is  the  person 
being  tested  to  be  asked  to  name  a  color.  In  a  large  class  of  students  one 
is  pretty  sure  to  find  some  who  are  more  or  less  color-blind.  The  common 
defects  are  for  red  and  green. 

Place  worsteds  on  a  white  background  in  a  good  light.  Select,  as  a 
test  color,  a  skein  of  light  green  color,  such  as  would  be  obtained  by  mix- 
ing a  pure  green  with  white.  Ask  the  examinee  to  select  and  pick  out 
from  the  heap  all  those  skeins  which  appear  to  him  to  be  of  the  same 
color,  whether  of  lighter  or  darker  shades.  A  color-blind  person  will 
select  amongst  others  some  of  the  confusion-colors,  e.g.,  pink,  yellow.  A 
colored  plate  showing  these  should  be  hung  up  in  the  room.  Any 
one  who  selects  all  the  greens  and  no  confusion-colors  has  normal  color 
vision.  If,  however,  one  or  more  confusion-colors  be  selected,  proceed  as 
follows  :  select  as  a  test  color  a  skein  of  pale  rose.  If  the  person  be  red- 
blind,  he  will  choose  blue  and  violet ;  if  green-blind,  gray  and  green. 

Select  a  bright  red  skein.  The  red-blind  will  select  green  and  brown ; 
the  green-blind  picks  out  reds  or  lighter  brown. 


338 


PRACTICAL    PHYSIOLOGY. 


339.    Practical  Hints  on  the  Care  of  the  Eyes.     The  eye 

is  an  exceedingly  delicate  and  sensitive  organ.  While  it  is  long- 
suffering,  its  endurance  has  a  limit.  Like  all  the  other  organs 
of  the  body,  the  eyes  are  better  for  moderate  and  rational  use. 
More  than  any  other  organ  they  require  attention  to  the  gen- 
eral health,  as  the  condition  of  the  skin,  exercise  in  the  open 
air,  good  food,  and  proper  habits  of  daily  living. 

The  tissues  of  the  eyes  are  peculiarly  sensitive  to  any  general 
influence.  Certain  constitutional  diseases,  like  rheumatism, 
lead-poisoning,  diphtheria,  and  measles  often  affect  the  eyes. 

Special  care  should  be 
taken  with  children's 
eyes  during  and  after 
an  attack  of  measles 
and  scarlet  fever.  The 
eyes  of  young  infants 
should  not  be  exposed 
to  glaring  lights  or  to 
the  direct  rays  of  the 
sun,  as  when  taken  out 
FIG.  136.  —  Showing  the  Relative  Position  of  in  baby  carriages. 

the  Lacrymal  Apparatus,  the  Eyeball,  and  the 
Eyelids. 


be 


Glasses    should 
worn    when    they    are 
A  failure  to 


A,  lacrymal  canals,  with  the  minute  orifices  represented 
as  two  black   dots  (puncta  lacrymalia)  to  the  right; 
B,   tendon   of    the   orbicularis   palpebrarum   muscle ;     do    this    USUally    CaUSCS 
apparently  under  B  is  seen   the  lacrymal  sac.      The 
minute  openings  of  the  Meibomian  glands  are  seen  on 
the  free  margins  of  the  eyelids.     Below  A  is  seen  a    fering. 
small  conical  elevation,  with  black  dots  (the  lacrymal 
papilla  or  caruncle). 


unnecessary  suf- 
It  is  far  from 
wise  to  postpone  as 
long  as  possible  the 
The  selection  and  proper  fitting  of 
glasses  call  for  the  combined  skill  of  both  the  physician 
and  the  optician.  Obstinate  headaches  are  often  caused  by 
defective  vision,  and  may  disappear  after  discontinuing  im- 
proper glasses. 


first   use    of   glasses. 


THE    SPECIAL    SENSES.  339 

The  habit  of  reading,  in  the  cars  or  elsewhere,  the  daily  paper 
and  poorly  printed  books,  with  their  blurred  and  indistinct 
type,  is  a  severe  strain  on  the  accommodation  apparatus  of  the 
eyes.  It  is  a  dangerous  practice  to  read  in  bed  at  night,  or 
while  lying  down  in  a  darkened  or  shaded  room.  This  is 
especially  true  during  recovery  from  illness.  The  muscles  of 
the  eyes  undergo  excessive  strain  in  accommodating  them- 
selves to  the  unnatural  position.  The  battered  type,  wood-pulp 
paper,  and  poor  presswork,  now  so  commonly  used  in  the  cheap 
editions  of  books  and  periodicals,  are  often  injurious  to  the 
eyesight. 

Reading-matter  should  not  be  held  nearer  to  the  eyes  than 
is  necessary  to  make  the  print  appear  perfectly  sharp  and  dis- 
tinct. No  print  should  be  read  continuously  that  cannot  be 
seen  clearly  at  about  eighteen  inches.  Those  who  read  music 
are  especially  liable  to  strain  the  eyes,  because  exact  vision  is 
required  to  follow  the  notes.  Persons  who  wear  glasses  for 
reading  should  be  careful  to  use  them  while  reading  music,  and 
good  light  is  necessary  to  avoid  any  undue  strain. 

After  reading  steadily  for  some  time,  the  eyes  should  be  rested 
by  closing  them  a  short  period  or  by  looking  at  some  distant 
object,  even  if  only  for  a  few  moments.  The  book,  the  sewing, 
and  work  generally,  should  be  held  as  far  from  the  eyes  as  is 
compatible  with  good  vision.  The  natural  tendency  is  to  re- 
verse this  rule.  We  should  never  read,  write,  sew,  stitch,  or 
otherwise  use  the  eyes  when  they  smart  or  tingle,  or  when  the 
sight  is  dim  or  blurred.  The  eyes  are  then  tired  and  need  a 
rest.  Much  injury  may  be  done  by  reading  in  twilight,  or  by 
artificial  light  in  the  early  morning,  and  by  reading  and  work- 
ing in  badly  lighted  and  ill-ventilated  rooms. 

Good  artificial  light  is  much  to  be  preferred  to  insufficient 
sunlight.  The  artificial  light  should  be  sufficiently  bright  and 
steady  ;  a  flickering  light  is  always  bad.  Riding  against  a 
strong  wind,  especially  on  a  bicycle,  may  prove  hurtful,  at  least 


34O  PRACTICAL  PHYSIOLOGY. 

for  eyes  that  are  inclined  to  any  kind  of  inflammation.  The 
light  reflected  from  snow  is  a  common  source  of  injury  to  the 
eyes.  It  is  a  wise  caution  in  passing  from  a  dark  room  to 
avoid  looking  immediately  at  the  sun,  an  incandescent  light, 
the  glistening  snow,  or  other  bright  objects. 

The  eyes  should  never  be  rubbed,  or  the  fingers  thrust  into 
them,1  and  much  less  when  they  are  irritated  by  any  foreign 
substance.  The  sooner  the  offending  substance  is  removed 
the  better. 

340.  Effect  of  Alcohol  upon  the  Eye.  The  earlier  and 
slighter  forms  of  injury  done  to  the  eye  by  the  use  of  intoxi- 
cants are  quite  familiar  :  the  watery  condition  of  the  eye  and  of 
the  lids,  and  the  red  and  bleared  aspect  of 
the  organ.  Both  are  the  result  of  chronic 
inflammation,  which  crowds  the  blood  into 
the  vessels  of  the  cornea,  making  them 
bloodshot  and  visible.  The  nerves  con- 
trolling the  circulation  of  the  eye  are 
partially  paralyzed,  and  thus  the  relaxed 

r  vessels  become  distended. 

But  more  serious  results  ensue.     Long 
use  of  intoxicants  produces  diseases  of 
the  retina,  involving  in  many  cases  marked 
FIG.  137.— Lacrymal  Can-   diminution  of  acuteness  as  well  as  quick- 

als,   Lacrymal   Sac,  and    ness    Qf    visiorij     and    at    times     distorted 
Nasal   Duct,  opened   by    .  /•/-,• 

their  Anterior  Portion,    -images  upon  the  surface  of  the  retina.    In 
other    instances,    the    congestion    of   the 

optic  nerve  is  so  serious  as  to  involve  a  progressive  wasting 
of  that  organ,  producing  at  first  a  hazy  dimness  of  vision 
which  gradually  becomes  worse  and  worse,  till  total  blindness 
may  ensue. 

1  The  Germans  have  a  quaint  proverb  that  one  should  never  rub  his  eye.  except 
with  his  elbows ! 


THE    SPECIAL    SENSES.  341 

It  is  beyond  question  that  a  wide  comparison  of  cases  by 
careful  observers  proves  that  a  large  fraction  of  those  who 
indulge  in  strong  drink  suffer  from  some  form  of  disease  of  the 
eye. 

341.  Effect  of  Tobacco  upon  Vision.     Tobacco,  in  its  dis- 
tribution   of    evil    effects,   does    not    neglect    the    senses   and 
especially  the  eye.     A  variety  of  vicious  results  is  produced. 
The  pungent  smoke  inflames  the  lids.     The  narcotic  dilates 
the  pupil,  causing  dimness  and  confusion  of  vision.     A  dis- 
eased condition  occurs  with  severe  pain  in  the  eye  followed  by 
impaired  vision. 

Oculists  speak  impressively  of  the  ill  effects  of  tobacco,  and 
especially  of  cigarettes,  upon  the  eyes  of  the  young.  They 
mention  a  well-known  disease,  tobacco  blindness,  usually  be- 
ginning with  color-blindness,  and  progressing  occasionally  with 
increasing  dimness  of  vision  to  entire  loss  of  sight.1 

342.  The  Sense  of  Hearing.     The  structure  of  the  human 
ear  is  much  more  complicated  than  is  generally  supposed.     It 
is  an  apparatus  constructed  to  respond  to  the  waves  of  sound. 
As  a  whole,  it  may  be  considered  a  peculiar  form  of  nerve- 
ending. 

1  "  The  deleterious  effect  of  tobacco  upon  eyesight  is  an  acknowledged  fact. 
The  Belgian  government  instituted  an  investigation  into  the  cause  of  the  prevalence 
of  color-blindness.  The  unanimous  verdict  of  the  experts  making  the  examination 
was  that  the  use  of  tobacco  was  one  of  the  principal  causes  of  this  defect  of  vision. 

"  The  dimness  of  sight  caused  by  alcohol  or  tobacco  has  long  been  clinically 
recognized,  although  not  until  recently  accurately  understood.  The  main  facts  can 
now  be  stated  with  much  assurance,  since  the  publication  of  an  article  by  Uhthoff 
which  leaves  little  more  to  be  said.  He  examined  one  thousand  patients  who  were 
detained  in  hospital  because  of  alcoholic  excess,  and  out  of  these  found  a  total  of  eye 
diseases  of  about  thirty  per  cent. 

"  Commonly  both  eyes  are  affected,  and  the  progress  of  the  disease  is  slow,  both 
in  culmination  and  in  recovery.  .  .  .  Treatment  demands  entire  abstinence."  — 
HENRY  D.  NOYES,  Professor  of  Otology  in  the  Bellevue  Hospital  Medical  College, 
New  York. 


342 


PRACTICAL    PHYSIOLOGY. 


The  external  ear  forms  only  a  part  of  a  most  elaborate  appa- 
ratus whereby  sound  waves  may  be  transmitted  inwards  to  the 
real  organ  of  hearing.  The  really  sensitive  part  of  the  ear, 
in  which  the  auditory  nerve  ends,  is  buried  for  protection  deep 
out  of  sight  in  the  bones  of  the  head ;  so  deep  that  sounds 
cannot  directly  affect  it.  Some  arrangement,  therefore,  is 
required  for  conducting  the  sounds  inwards  to  this  true  organ. 

In  studying  the  structure 
of  the  ear,  and  how  it  is 
fitted  to  respond  to  sonorous 
vibrations,  we  may  divide  it 
into  three  parts  :  the  sound- 
conducting  part,  known  as 
the  external  ear,  the  middle 
ear,  and  the  deeply  placed 
nerve  portion,  the  inner  ear. 

343.  The  External  Ear. 
The  external  ear  consists  of 
an  expanded  portion  known 
as  the  pinna  or  auricle,  and 
of  a  passage,  the  auditory 
canal  or  meatus,  leading  in- 
wards from  it.  The  surface 
of  the  auricle  is  convoluted  to  collect  and  transmit  the 
vibrations  of  air  by  which  sound  is  produced :  the  auditory 
canal  conducts  these  vibrations  to  the  tympanic  membrane. 
Many  animals  move  the  auricle  in  the  direction  of  the  sound. 
Thus  the  horse  pricks  up  its  ears  when  it  hears  a  noise,  the 
better  to  judge  of  the  direction  of  sounds.1 

1  "  The  student  who  will  take  a  little  trouble  in  noticing  the  ears  of  the  persons 
whom  he  meets  from  day  to  day  will  be  greatly  interested  and  surprised  to  see  how 
much  the  auricle  varies.  It  may  be  a  thick  and  clumsy  ear  or  a  beautifully  delicate 
one ;  long  and  narrow  or  short  and  broad ;  may  have  a  neatly  formed  and  distinct 
lobule,  or  one  that  is  heavy,  ungainly,  and  united  to  the  cheek  so  as  hardly  to  form  a 


FIG.  138. —  The  Pinna,  or  Auricle. 


THE    SPECIAL    SENSES.  343 

The  external  auditory  meatus,  the  passage  to  the  middle  ear, 
is  curved  and  is  about  an  inch  and  a  quarter  long.  Near  its 
outer  portion  are  a  number  of  fine  hairs  slanting  outwards  to 
prevent  the  entrance  of  insects.  Embedded  in  the  deeper 
parts  of  the  canal  are  glands  which  secrete  the  cerumen,  or  ear- 
wax,  which  keeps  the  canal  moist,  and  helps  to  protect  it  against 
foreign  bodies  and  insects.  As  the  result  of  a  cold,  this  wax 
may  collect  in  sufficient  quantities  to  block  the  passage,  and 
to  diminish  to  a  considerable  extent  the  power  of  hearing. 

344.  The  Middle  Ear.  At  the  inner  end  of  the  outer  ear 
passage  is  the  tympanum,  known  as  "the  drum  of  the  ear." 
It  is  a  thin,  oval  membrane,  stretched  at  an  angle  across  the 
deep  end  of  the  passage,  which  it  completely  closes.  The 
tympanum  is  thus  a  partition  between  the  passage  of  the  outer 
ear  and  the  cavity  of  the  middle  ear.  On  its  inner  side  is  a 
small  air  chamber  in  the  petrous  portion  of  the  temporal  bone, 
called  the  cavity  of  the  tympanum.  Its  bony  walls  are  lined 
with  mucous  membrane  similar  to  that  lining  the  nose,  mouth, 
and  throat.  On  the  inner  wall  of  the  tympanum  are  two  open- 
ings, the  round  window,  or  foramen  rotundum,  and  the  oval 
window,  or  foramen  ovale. 

The  tympanic  cavity  communicates  with  the  back  part  of 
the  throat,  by  the  Eustachian  tube.  This  tube  is  about  one 
and  a  half  inches  long  and  lined  with  mucous  membrane 
similar  to  that  of  the  tympanic  chamber  and  the  throat.  This 
passage  is  usually  closed,  but  is  opened  in  the  act  of  swallowing. 
In  health  there  is  no  communication  between  the  chamber  of  the 
middle  ear  and  the  outside,  except  by  the  Eustachian  tube.  Thus 
a  throat  cold,  with  redness  and  swelling  of  the  mucous  mem- 
brane, is  usually  accompanied  with  some  degree  of  deafness, 

separate  part  of  the  auricle  ;  may  hug  the  head  closely  or  flare  outward  so  as  to  form 
almost  two  wings  to  the  head.  In  art,  and  especially  in  medallion  portraits,  in  which 
the  ear  is  a  marked  (because  central)  feature,  the  auricle  is  of  great  importance." 
—  WILLIAM  W.  KEEN,  M.D.,  editor  of  Gray's  Anatomy. 


344 


PRACTICAL    PHYSIOLOGY. 


because  the  swelling    may  block  the  lumen  of  the  tube,  and 
thus  prevent  the  free  passage  of  air  to  and  fro. 

A  most  curious  feature  of  the  ear  is  the  chain  of  tiny  movable 
bones  which  stretch  across  the  cavity  of  the  middle  ear.  They 
connect  the  tympanic  membrane  with  the  labyrinth,  and  serve 
to  convey  the  vibrations  communicated  to  the  membrane  across 
the  cavity  of  the  tympanum  to  the  internal  ear.  These  bones 


FIG.  139.  —  General  View  of  the  Organ  of  Hearing. 

A,  pinna;  B,  cavity  of  the  concha,  showing  the  orifices  of  a  great  number  of  sebaceous 
glands ;  C,  external  auditory  meatus  ;  D,  membrana  tympani ;  F,  incus  ;  H,  malleus ; 
K,  handle  of  malleus  applied  to  the  internal  surface  of  the  membrana  tympani ;  L, 
tensor  tympani  muscle;  between  M  and  K  is  the  tympanic  cavity ;  N,  Eustachian 
tube ;  O,  P,  semicircular  canals ;  R,  internal  auditory  canal ;  S,  large  nerve  given 
off  from  the  facial  ganglion ;  T,  facial  and  auditory  nerves. 

are  three  in  number,  and  from  their  shape  are  called  the 
malleus,  or  hammer ;  incus,  or  anvil ;  and  stapes,  or  stirrup. 
The  hammer  is  attached  by  its  long  handle  to  the  inner  sur- 
face of  the  drum  of  the  ear.  The  round  head  is  connected 
with  the  anvil  by  a  movable  joint,  while  the  long  projection  of 
the  anvil  is  similarly  connected  with  the  stirrup  bone.  The 
plate  of  the  stirrup  is  fixed  by  a  membrane  into  the  oval  window 
of  the  inner  wall  of  the  tympanic  chamber. 


THE    SPECIAL    SENSES. 


345 


1,  malleus,  or  hammer; 
2,  incus,  or  anvil ;  3, 
tapes,  or  stirrup. 


These  little  bones  are  connected  with  each  other  and  the 
tympanum  by  ligaments  and  moved  by  three  tiny  muscles. 
Two  are  attached  to  the  hammer,  and  tighten  and  relax  the 
drum  ;  the  other  is  attached  to  the  stirrup,  and  prevents  it 
from  being  pushed  too  deeply  into  the 
oval  window. 

345.  The  Internal  Ear.  This  forms  one 
of  the  most  delicate  and  complex  pieces  of 
mechanism  in  the  whole  body.  It  is  that 
portion  of  the  organ  which  receives  the  im- 

-.-...       ..          .  FIG.  140. —  Ear-Bones. 

pression  of  sound,  and  carries  it  directly  to        (Anterior  view.) 
the  seat  of  consciousness  in  the  brain.     We 
are  then  able  to  say  that  we  hear. 

The  internal  ear,  or  bony  labyrinth, 
consists  of  three  distinct  parts,  or  variously  shaped  chambers, 
hollowed  out  in  the  temporal  bone,  —  the  vestibule,  the  semi- 
circular canals,  and  the  cochlea,  or  snail's  shell. 

The  vestibule  is  the 
common  cavity  with 
which  all  the  other 
portions  of  the  labyrinth 
connect.  It  is  an  oval- 
shaped  chamber,  about  £ 
of  an  inch  in  diameter, 
occupying  the  middle  part 
of  the  internal  ear.  It  is 
on  the  inner  side  of  the 
oval  window,  which  was 
closed,  as  we  have  seen, 

FIG.  141.-  A  Cast  of  the  External  Auditory      fe     the  ^  bone     From 

Canal.     (Posterior  view.)  •'  r 

one  side  of  this  vestibule, 

or  central  hall,   the    three  semicircular   canals    pass  off,   and 
from  the  other  side,  the  cochlea. 


34-6  PRACTICAL    PHYSIOLOGY. 

The  three  semicircular  canals,  so  called  from  their  shape, 
are  simply  bony  tubes  about  ^G  of  an  inch  in  width,  making 
a  curve  of  about  J  of  an  inch  in  diameter.  They  pass  out 
from  the  vestibule,  and  after  bending  around  somewhat  like  a 
hoop,  they  return  again  to  the  vestibule.  Each  bony  canal 
contains  within  it  a  membranous  canal,  at  the  end  of  which  it 
is  dilated  to  form  an  ampulla, 

Experiment  157.  To  vibrate  the  tympanic  membrane  and  the  little  ear- 
bones.  Shut  the  mouth,  and  pinch  the  nose  tightly.  Try  to  force  air  through 
the  nose.  The  air  dilates  the  Eustachian  tube,  and  is  forced  into  the  ear- 
drum. The  distinct  crackle,  or  clicking  sound,  is  due  to  the  movement  of 
the  ear-bones  and  the  tympanic  membrane. 

The  cochlea,  or  snail's  shell,  is  another  chamber  hollowed 
out  in  the  solid  bone.  It  is  coiled  on  itself  somewhat  like  a 
snail's  shell.  There  is  a  central  pillar,  around  which  winds  a 
long  spiral  canal.  One  passage  from  the  cochlea  opens  directly 
into  the  vestibule  ;  the  other  leads  to  the  chamber  of  the  mid- 
dle ear,  and  is  separated  from  it  by  the  little  round  window 
already  described. 

The  cochlea  contains  thousands  of  the  most  minute  cords, 
known  as  the  fibers  or  organ  of  Corti.1  Under  the  microscope 
they  present  the  appearance  of  the  keyboard  of  a  piano. 
These  fibers  appear  to  vibrate  in  sympathy  with  the  countless 
shades  of  sounds  which  daily  penetrate  the  ear.  From  the 
hair-like  processes  on  these  tightly  stretched  fibers,  auditory 
impulses  appear  to  be  transmitted  to  the  brain. 

1  The  organ  of  Corti  is  a  very  complicated  structure  which  it  is  needless  to 
describe  in  this  connection.  It  consists  essentially  of  modified  ephithelial  cells 
floated  upon  the  auditory  epithelium,  or  basilar  membrane,  of  the  cochlea.  There 
is  a  series  of  fibers,  each  made  of  two  parts  sloped  against  each  other  like  the  rafters 
of  a  roof.  It  is  estimated  that  there  are  no  less  than  3000  of  these  arches  in  the 
human  ear,  placed  side  by  side  in  a  continuous  series  along  the  whole  length  of  the 
basilar  membrane.  Resting  on  these  arches  are  numbers  of  conical  epithelial  cells, 
from  the  free  surface  of  which  bundles  of  stiff  hairs  (cilia)  project.  The  fact  that 
these  hair-cells  are  connected  with  the  fibers  of  the  cochlear  division  of  the  auditory 
nerve  suggests  that  they  must  play  an  important  part  in  auditory  sensation. 


THE    SPECIAL    SENSES. 


347 


The  tubes  and  chambers  of  the  inner  ear  enclose  and  pro- 
tect a  delicate  membranous  sac  of  exactly  the  same  shape  as 
themselves.  Between  the  bony  walls  of  the  passages  and  the 
membranous  bag  inside  is  a  thin,  clear  fluid,  the  perilymph. 
The  membranous  bag  itself  contains  a  similar  fluid,  the  endo- 
lymph.  In  this  fluid  are  found  some  minute  crystals  of  lime 
like  tiny  particles  of  sand,  called  otoliths,  or  ear-stones.  Every 

movement  of  the  fluid  itself 
throws  these  grains  from  side 
to  side. 

The  auditory  nerve,  or 
nerve  of  hearing,  passes  to 
the  inner  ear,  through  a  pas- 
sage in  the  solid  bone  of  the 
skull.  Its  minute  filaments 
spread  at  last  over  the  inner 
walls  of  the  membranous  laby- 
FIG.  142.  — Bony  internal  Ear  of  the  rinth  in  two  branches,  —  one 

Right  Side.     (Magnified;    the   upper  •         tQ  the  vestibule  and  the 

figure  of  the  natural  size.) 

.   .  ,     .,  ,  .    Q  _  _       .    ampullae  at  the  ends   of   the 

A,  oval  window  (foramen  ovale) ;  B,  C,  D,  semi- 
circular canals;  *  represents  the  bulging   semicircular  canals,  the  other 

part  (ampulla)  of  each  canal;   E,  F,  G  coch-    leadi          t       ^       cochlea. 
lea;  H,  round  window  (foramen  rotundum). 

346.  Mechanism  of  Hearing.  Waves  of  sound  reach  the 
ear,  and  are  directed  by  the  concha  to  the  external  passage, 
at  the  end  of  which  they  reach  the  tympanic  membrane. 
When  the  sound-waves  beat  upon  this  thin  membrane,  it  is 
thrown  into  vibration,  reproducing  in  its  movements  the  char- 
acter of  the  air-vibrations  that  have  fallen  upon  it. 

Now  the  vibrations  of  the  tympanic  membrane  are  passed 
along  the  chain  of  bones  attached  to  its  inner  surface  and 
reach  the  stirrup  bone.  The  stirrup  now  performs  a  to-and- 
fro  movement  at  the  oval  window,  passing  the  auditory  impulse 
inwards  to  the  internal  ear. 


34-8  PRACTICAL    PHYSIOLOGY. 

Every  time  the  stirrup  bone  is  pushed  in  and  drawn  out  of 
the  oval  window,  the  watery  fluid  (the  perilymph)  in  the  vesti- 
bule and  inner  ear  is  set  in  motion  more  or  less  violently, 
according  to  the  intensity  of  the  sound.  The  membranous 
labyrinth  occupies  the  central  portion  of  the  vestibule  and  the 
passages  leading  from  it.  When,  therefore,  the  perilymph  is 
shaken  it  communicates  the  impulse  to  the  fluid  (endolymph) 
contained  in  the  inner  membranous  bag.  The  endolymph  and 
the  tiny  grains  of  ear-sand  now  perform  their  part  in  this 
marvelous  and  complex  mechanism.  They  are  driven  against 
the  sides  of  the  membranous  bag,  and  so  strike  the  ends  of 
the  nerves  of  hearing,  which  transmit  the  auditory  impulses 
to  the  seat  of  sensation  in  the  brain. 

It  is  in  the  seat  of  sensation  in  the  brain  called  the  sensorium 
that  the  various  auditory  impulses  received  from  different  parts 
of  the  inner  ear  are  fused  into  one,  and  interpreted  as  sounds. 
It  is  the  extent  of  the  vibrations  that  determines  the  loudness 
of  the  sound  ;  the  number  of  them  that  determines  the  pitch. 

Experiment  158.  Hold  a  ticking  watch  between  the  teeth,  or  touch 
the  upper  incisors  with  a  vibrating  tuning-fork  ;  close  both  ears,  and  observe 
that  the  ticking  or  vibration  is  heard  louder.  Unstop  one  ear,  and  ob- 
serve that  the  ticking  or  vibration  is  heard  loudest  in  the  stopped  ear. 

Experiment  159.  Hold  a'vibrating  tuning-fork  on  the  incisor  teeth  until 
you  cannot  hear  it  sounding.  Close  one  or  both  ears,  and  you  will  hear  it. 

Experiment  160.  Listen  to  a  ticking  watch  or  a  tuning-fork  kept  vibrat- 
ing electrically.  Close  the  mouth  and  nostrils,  and  take  either  a  deep 
inspiration  or  deep  expiration,  so  as  to  alter  the  tension  of  the  air  in  the 
tympanum ;  in  both  cases  the  sound  is  diminished. 

Experiment  161.  With  a  blindfolded  person  test  his  sense  of  the  direc- 
tion of  sound,  e.g.,  by  clicking  two  coins  together.  It  is  very  imperfect. 
Let  a  person  press  both  auricles  against  the  side  of  the  head,  and  hold  both 
hands  vertically  in  front  of  each  meatus.  On  a  person  making  a  sound  in 
front,  the  observed  person  will  refer  it  to  a  position  behind  him. 


THE    SPECIAL    SENSES.  349 

347.  Practical  Hints  on  the  Care  of  the  Ear.  This  very 
delicate  and  complicated  organ  is  often  neglected  when  skilled 
treatment  is  urgently  needed,  and  it  is  often  ignorantly  and 
carelessly  tampered  with  when  it  should  be  let  alone. 

Never  insert  into  the  ear  canal  the  corners  of  towels,  ear 
spoons,  the  ends  of  toothpicks,  hairpins,  or  any  other  pointed 
instruments.  It  is  a  needless  and  dangerous  practice,  usually 


VESTIBULE  WITH  OPENINGS 
,'OF  SEMICIRCULAR  CANALS 


SCALA  VESTIBULI 

^V— /-  INCUS 
—/_./-  MALLEUS 

-STAPES 


EXT.  AUD.    MEATUS. 
— MEMBRANA  TYMPANI 


SCALA  TVMPANI  

EUSTACHIAN  TUBE 

FIG.  143. —  Diagram  of  the  Middle  and  Internal  Ear. 

causing,  in  time,  some  form  of  inflammation.  The  abrasion  of 
the  skin  in  the  canal  thus  produced  affords  a  favorable  soil 
for  the  growth  of  vegetable  parasites. 

This,  in  turn,  may  lead  to  a  chronic  inflammation  of  the 
canal  and  of  the  tympanic  membrane.  Again,  there  is  always 
risk  that  the  elbow  may  be  jogged  and  the  instrument  pushed 
through  the  drum-head.  There  is,  of  course,  a  natural  impulse 
to  relieve  the  itching  of  the  ear.  This  should  be  done  with  the 
tips  of  the  fingers  or  not  at  all. 

The  popular  notion  that  something  should  be  put  into  the 
ear  to  cure  toothache  is  erroneous.  This  treatment  does  not 
cure  a  toothache,  and  may  lead  to  an  injury  to  the  delicate 
parts  of  the  ear.  A  piece  of  absorbent  cotton,  carefully  inserted 
into  the  ear,  may  be  worn  out  of  doors,  when  the  cold  air 
causes  pain,  but  should  be  removed  on  coming  into  the  house. 


3  SO  PRACTICAL    PHYSIOLOGY. 

Frequent  bathing  in  the  cold  water  of  ponds  and  rivers  is  liable 
to  injure  both  the  ears  and  the  general  health.  In  salt-water 
bathing,  the  force  of  the  waves  striking  against  the  ears  often 
leads  to  earache,  long-continued  inflammation,  or  defective 
hearing ;  to  diminish  this  risk,  insert  into  the  ears  a  small 
plug  of  absorbent  cotton. 

The  ears  are  often  carelessly  exposed  to  cold  water  and 
inclement  weather.  Very  cold  water  should  never  be  used  to 
bathe  the  ears  and  nostrils.  Bathe  moderately  and  gently  in 
lukewarm  water,  using  a  wash-rag  in  preference  to  a  sponge  ; 
dry  gently  and  thoroughly.  Children's  ears  are  often  rudely 
washed,  especially  in  the  auditory  canal.  This  is  not  at  all 
necessary  to  cleanliness,  and  may  result  in  a  local  inflammation. 

Never  shout  suddenly  in  a  per- 
son's ear.    The  ear  is  not  prepared 
for  the   shock,  and  deafness  has 
occasionally  resulted.      A  sudden 
explosion,  the  noise  of  a  cannon, 
may  burst  the  drum-head,  especially 
FIG.  144.  — Section  of  Cochlea.       if  the  Eustachian  tube  be  closed 
From  A  straight  downwards  is  the  direo    at  the  time.     During  heavy  can- 
tion  of  the  central  column,  to  which    nonading,  soldiers  are    taught   to 

E  points.     B  points  to  the  projecting 

ridge,  almost  dividing  the  canal  of    keep  the  mouth  open  to  allow  an 

the  tube  into  an  upper  compartment      equal    tension    of    air. 
(D),  and  a  lower  (C). 

Insects    may   gam  entrance    to 

the  ears  and  occasion  annoyance,  pain,  and  fright,  perhaps 
leading  to  vomiting,  even  to  convulsions,  with  nervous  children. 
A  lighted  lamp  held  at  the  entrance  of  the  ear  will  often  induce 
the  offending  insect  to  crawl  out  towards  the  light.  A  few 
drops  of  warm  water,  sweet  oil,  or  molasses,  dropped  into  the 
ear,  will  help  remove  the  intruder. 

When  a  discharge  occurs  from  the  ears,  it  is  not  best  to 
plug  them  with  cotton  wads.  It  only  keeps  in  what  should  be 
got  rid  of.  Do  not  go  to  sleep  with  the  head  on  a  window 


THE    SPECIAL    SENSES.  35 1 

sill  or  in  any  position,  with  the  ears  exposed  to  draughts  of 
cold  or  damp  air. 

No  effort  should  be  made  to  remove  the  ear  wax  unless  it 
accumulates  unduly.  The  skin  of  the  canal  grows  outward, 
and  the  extra  wax  and  dust  will  be  naturally  carried  out,  if  let 
alone.  Never  employ  any  of  the  many  articles  or  "  drops," 
advertised  to  cure  deafness.  Neuralgic  pain  in  the  canal, 
usually  classed  as  earache,  may  be  due  to  decayed  or  improp- 
erly filled  teeth. 

Quinine,  so  generally  used  in  its  many  preparations  for 
malaria,  causes  a  peculiar  ringing  or  buzzing  in  the  ears. 
This  is  a  warning  that  it  should  be  taken  in  smaller  doses,  or 
perhaps  stopped  for  a  time.  In  some  cases  quinine  may  pro- 
duce temporary  deafness. 

The  practice  of  snuffing  up  cold  water  into  the  nostrils  is 
occasionally  followed  by  an  acute  inflammation  of  the  middle 
ear,  some  of  the  water  finding  its  way  through  the  Eustachian 
tube  into  this  part  of  the  organ  of  hearing.  The  nasal  douche, 
so  often  advised  as  a  home  remedy  for  nasal  catarrh,  should 
be  used  only  with  great  caution,  and  always  in  accordance  with 
detailed  directions  from  a  physician. 

348.  Effect  of  Tobacco  upon  the  Hearing.  The  sense  of 
hearing  is  often  injured  by  the  use  of  tobacco.  The  irritating 
smoke  filling  all  the  inner  cavity  of  the  mouth  and  throat, 
readily  finds  its  way  up  the  Eustachian  tube,  dries  the  mem- 
brane, and  irritates  or  inflames  the  delicate  mechanism  of  the 
inner  ear.  Thus  may  be  produced  a  variety  of  serious  aural 
disturbances,  such  as  unnatural  noises,  whistling,  and  roaring, 
followed  oftentimes  by  a  partial  loss  of  hearing. 

Hearing  may  be  impaired  by  the  use  of  alcoholic  beverages. 
Alcohol  inflames  the  mucous  membrane  of  the  throat,  then  by 
its  nearness  the  lining  of  the  Eustachian  tube,  and  finally  may 
injure  the  delicate  apparatus  of  the  internal  ear. 


352  PRACTICAL    PHYSIOLOGY. 


ADDITIONAL   EXPERIMENTS. 

Experiment  162.  Use  a  small  pair  of  wooden  compasses,  or  an  ordi- 
nary pair  of  dividers  with  their  points  guarded  by  a  small  piece  of  cork. 
Apply  the  points  of  the  compasses  lightly  and  simultaneously  to  different 
parts  of  the  body,  and  ascertain  at  what  distance  apart  the  points  are  felt 
as  two.  The  following  is  the  order  of  sensibility  :  tip  of  tongue,  tip  of  the 
middle  finger,  palm,  forehead,  and  back  of  hand. 

Experiment  163.  Test  as  in  preceding  experiment  the  skin  of  the  arm, 
beginning  at  the  shoulder  and  passing  downwards.  Observe  that  the  sensi- 
bility is  greater  as  one  tests  towards  the  fingers,  and  also  in  the  transverse 
than  in  the  long  axis  of  the  limb.  In  all  cases  compare  the  results  obtained 
on  both  sides  of  the  body. 

Experiment  164.  By  means  of  a  spray-producer,  spray  the  back  of  the 
hand  with  ether,  and  observe  how  the  sensibility  is  abolished. 

Experiment  165.  Touch  your  forehead  with  your  forefinger;  the  finger 
appears  to  feel  the  contact,  but  on  rubbing  the  forefinger  rapidly  over  the 
forehead,  it  is  the  latter  which  is  interpreted  as  "  feeling  "  the  finger. 

Experiment  166.  Generally  speaking,  the  sensation  of  touch  is  referred 
to  the  cutaneous  surfaces.  In  certain  cases,  however,  it  is  referred  even 
beyond  this.  Holding  firmly  in  one  hand  a  cane  or  a  pencil,  touch  an 
object  therewith  ;  the  sensation  is  referred  to  the  extremity  of  the  cane  or 
pencil. 

If,  however,  the  cane  or  pencil  be  held  loosely  in  one's  hand,  one  experi- 
ences two  sensations:  one  corresponding  to  the  object  touched,  and  the 
other  due  to  the  contact  of  the  rod  with  the  skin.  The  process  of  mastica- 
tion affords  a  good  example  of  the  reference  of  sensations  to  and  beyond 
the  periphery  of  the  body. 

Experiment  167.  Prepare  a  strong  solution  of  sulphate  of  quinine 
with  the  aid  of  a  little  sulphuric  acid  to  dissolve  it  (bitter),  a  five-per-cent 
solution  of  sugar  (sweet},  a  ten-per-cent  solution  of  common  salt  (saline], 
and  a  one-per-cent  solution  of  acetic  acid  (acid).  Wipe  the  tongue  dry, 
and  lay  on  its  tip  a  crystal  of  sugar.  It  is  not  tasted  until  it  is  dissolved. 

Experiment  168.  Apply  a  crystal  of  sugar  to  the  tip,  and  another  to  the 
back  of  the  tongue.  The  sweet  taste  is  more  pronounced  at  the  tip. 


THE    SPECIAL    SENSES.  353 

Experiment  169.  Repeat  the  process  with  sulphate  of  quinine  in  solu- 
tion. It  is  scarcely  tasted  on  the  tip,  but  is  tasted  immediately  on  the  back 
part  of  the  tongue.  Test  where  salines  and  acids  are  tasted  most  acutely. 

Experiment  170.  To  illustrate  the  muscular  sense.  Take  two  equal 
iron  or  lead  weights  ;  heat  one  and  leave  the  other  cold.  The  cold  weight 
will  feel  the  heavier. 

Experiment  171.  Place  a  thin  disk  of  cold  lead,  the  size  of  a  silver 
dollar,  on  the  forehead  of  a  person  whose  eyes  are  closed  ;  remove  the  disk, 
and  on  the  same  spot  place  two  warm  disks  of  equal  size.  The  person  will 
judge  the  latter  to  be  about  the  same  weight,  or  lighter,  than  the  single 
cold  disk. 

Experiment  172.  Compare  two  similar  wooden  disks,  and  let  the  di- 
ameter of  one  be  slightly  greater  than  that  of  the  other.  Heat  the  smaller 
one  to  over  120°  F.,  and  it  will  be  judged  heavier  than  the  larger  cold  one. 

Experiment  173.  To  illustrate  the  influence  of  excitation  of  one  sense 
organ  on  the  other  sense  organs.  Small  colored  patches  the  shape  and  color 
of  which  are  not  distinctly  visible  may  become  so  when  a  tuning-fork  is 
kept  vibrating  near  the  ears.  In  other  individuals  the  visual  impressions 
are  diminished  by  the  same  process. 

On  listening  to  the  ticking  of  a  watch,  the  ticking^sounds  feebler  or 
louder  on  looking  at  a  source  of  light  through  glasses  of  different  colors. 

If  the  finger  be  placed  in  cold  or  warm  water  the  temperature  appears 
to  rise  when  a  red  glass  is  held  in  front  of  the  eyes. 

Experiment  174.  Formation  of  an  in-verted  image  on  the  retina.  Take 
a  freshly  removed  ox-eye  ;  dissect  the  sclerotic  from  that  part  of  its  poste- 
rior segment  near  the  optic  nerve.  Roll  up  a  piece  of  blackened  paper  in 
the  form  of  a  tube,  black  surface  innermost,  and  place  the  eye  in  it  with 
the  cornea  directed  forward.  Look  at  an  object  — e.g.,  a  candle-flame  — 
and  observe  the  inverted  image  of  the  flame  shining  through  the  retina  and 
choroid,  and  notice  how  the  image  moves  when  the  candle  is  moved. 

Experiment  175.  Focus  a  candle-flame  or  other  object  on  the  ground- 
glass  plate  of  an  ordinary  photographic  camera,  and  observe  the  small 
inverted  image. 

Experiment  176.  To  illustrate  spherical  aberration.  Make  a  pin-hole 
in  a  blackened  piece  of  cardboard ;  look  at  a  light  placed  at  a  greater  dis- 
tance than  the  normal  distance  of  accommodation.  One  will  see  a  radiate 
figure  with  four  to  eight  radii.  The  figures  obtained  from  opposite  eyes 
will  probably  differ  in  shape. 


354  PRACTICAL    PHYSIOLOGY. 


Experiment  177.  Hold  a  thin  wooden  rod  or  pencil  about  a  foot  from 
the  eyes  and  look  at  a  distant  object.  Note  that  the  object  appears  double. 
Close  the  right  eye;  the  left  image  disappears,  and  vice  versa. 

Experiment  178.  To  show  the  movements  of  the  iris.  It  is  an  extremely 
beautiful  experiment,  and  one  that  can  easily  be  made.  Look  through  a 
pin-hole  in  a  card  at  a  uniform  white  surface  as  the  white  shade  of  an 
ordinary  reading-lamp.  With  the  right  eye  look  through  the  pin-hole, 
the  left  eye  being  closed.  Note  the  size  of  the  (slightly  dull)  circular  visual 
field.  Open  the  left  eye,  the  field  becomes  brighter  and  smaller  (con- 
traction of  pupil) ;  close  the  left  eye,  after  an  appreciable  time,  the  field 
(now  slightly  dull)  is  seen  gradually  to  expand.  One  can  thus  see  and 
observe  the  rate  of  movements  of  his  own  iris. 

Experiment  179.  To  show  the  blind  spot.  The  left  eye  being  shut,  let 
the  right  eye  be  fixed  upon  the  cross  as  in  Fig.  145.  When  the  book  is 


FIG. 145. 

held  at  arm's  length,  both  cross  and  round  spot  will  be  visible  ;  but  if  the 
book  be  brought  to  about  8  inches  from  the  eye,  the  gaze  being  kept 
steadily  upon  the  cross,  the  round  spot  will  at  first  disappear,  but  as  the 
book  is  brought  still  nearer  both  cross  and  round  spot  will  again  be  seen. 

Experiment  180.     To  illustrate  the  duration  of  retinal  impressions.    On  a 
circular  white  disk,  about  halfway  between  the  center  and  circumference, 

fix  a  small,  black,  oblong  disk,  and  rapidly 
rotate  it  by  means  of  a  rotating  wheel. 
There  appears  a  ring  of  gray  on  the  black, 
showing  that  the  impression  on  the  retina 
lasts  a  certain  time. 

A  B  Experiment  x8x.      Mark   off  a  round 

FIG.  146. Optic  Disks.  piece  of  cardboard  into  black  and  white 

sectors  as  in  A  (Fig.  146).     Attach  it  so  as 
The  disk  A,  having  black  and  white 

sectors,  when  rotated  rapidly  gives    to  rotate  *  rapidly,  as  on  a  sewing  machine, 
an  even  gray  tint  as  in  B.  An  even  gray  tint  will  be  produced  as  in  B. 

Experiment  182.      To  illustrate  imperfect  visual  judgments.     Make  three 
round  black  dots,  A,  B,  C,  of  the  same  size,  in  the  same  line,  and  let  A  and 


THE    SPECIAL    SENSES. 


355 


C  be  equidistant  from  B.    Between  A  and  B  make  several  more  dots  of  the 
same  size.     A  and  B  will  then  appear  to  be  farther  apart  than  B  and  C. 


For  the  same  reason,  of  two  squares  absolutely  identical  in  size,  one 
marked  with  alternately  clear  and  dark  cross-bands,  and  the  other  with 
alternately  clear  and  dark  upright  markings,  the  former  will  appear  broader 
and  the  latter  higher  than  the  other. 

Experiment  183.  Make  on  a  white  card  two  squares  of  equal  size. 
Across  the  one  draw  horizontal  lines  at  equal  distances,  and  in  the  other 
make  similar  vertical  lines.  Hold  them  at  some  distance.  The  one  with 
horizontal  lines  appears  higher  than  it  really  is,  while  the  one  with  vertical 
lines  appears  broader,  i.e.,  both  appear  oblong. 

Experiment  184.     Look  at  the  row  of  letters  (S)  and  figures  (8).     To 
SSSSSSSS  88888888 

some  the  upper  halves  of  the  letters  and  figures  may  appear  to  be  of  the 
same  size  as  the  lower  halves,  to  others  the  lower  halves  may  appear  larger. 
Hold  the  figure  upside  down,  and  observe 
that  there  is  a  considerable  difference  be- 
tween the  two,  the  lower  halves  being  consider- 
ably larger. 


B 


Experiment  185.  To  illustrate  imperfect 
visual  judgment.  The  length  of  a  line  appears 
to  vary  according  to  the  angle  and  direction 
of  certain  other  lines  in  relation  to  it  (Fig. 
147).  The  length  of  the  two  vertical  lines  is 
the  same,  yet  B  appears  much  longer  than  A. 


Experiment  186.  In  indirect  vision  the 
appreciation  of  direction  is  still  more  imperfect. 
While  leaning  on  a  large  table,  fix  a  point  on 
the  table,  and  then  try  to  arrange  three  small  pieces  of  colored  paper  in  a 
straight  line.  Invariably,  the  papers,  being  at  a  distance  from  the  fixation- 
point,  and  being  seen  by  indirect  vision,  are  arranged,  not  in  a  straight  line, 
but  in  the  arc  of  a  circle  with  a  long  radius. 


FIG.  147.—  To  show  False 
Estimate  of  Size. 


CHAPTER    XII. 
THE    THROAT    AND   THE    VOICE. 

349.  The  Throat.  The  throat  is  a  double  highway,  as  it 
were,  through  which  the  air  we  breathe  traverses  the  larynx  on 
its  way  to  the  lungs,  and  through  which  the  food  we  swallow 
reaches  the  oesophagus  on  its  passage  to  the  stomach.  It  is, 
therefore,  a  very  important  region  of  the  body,  being  con- 
cerned in  the  great  acts  of  respiration  and  digestion. 

The  throat  is  enclosed  and  protected  by  various  muscles 
and  bony  structures,  along  which  run  the  great  blood-vessels 
that  supply  the  head,  and  the  great  nerve  trunks  that  pass 
from  the  brain  to  the  parts  below. 

We  have  already  described  the  food  passages  (Chapter  VI.) 
and  the  air  passages  (Chapter  VIII.). 

To  get  a  correct  idea  of  the  throat  we  should  look  into  the 
wide-open  mouth  of  some  friend.  Depressing  the  tongue 
we  can  readily  see  the  back  wall  of  the  pharynx,  which  is 
common  to  the  two  main  avenues  leading  to  the  lungs  and  the 
stomach.  Above,  we  notice  the  air  passages,  which  lead  to 
the  posterior  cavities  of  the  nose.  We  have  already  described 
the  hard  palate,  the  soft  palate,  the  uvula,  and  the  tonsils 
(Fig.  46). 

On  looking  directly  beyond  these  organs,  we  see  the  begin- 
ning of  the  downward  passage,  —  the  pharynx.  If  now  the 
tongue  be  forcibly  drawn  forward,  a  curved  ridge  may  be  seen 
behind  it.  This  is  the  epiglottis,  which,  as  we  have  already 
learned  shuts  down,  like  the  lid  of  a  box,  over  the  top  of  the 
larynx  (sees.  137  and  203). 

The  throat  is  lined  with  mucous  membrane  covered  with  ciliated 
epithelium,  which  secretes  a  lubricating  fluid  which  keeps  the 


THE    THROAT    AND    THE    VOICE. 


357 


parts  moist  and  pliable.  An  excess  of  this  secretion  forms  a 
thick,  tenacious  mass  of  mucus,  which  irritates  the  passages  and 
gives  rise  to  efforts  of  hawking  and  coughing  to  get  rid  of  it. 


350.  The  Larynx.  The  larynx,  the  essential  organ  of 
voice,  forms  the  box-like  top  of  the  windpipe.  It  is  built  of 
variously  shaped  cartilages,  connected 
by  ligaments.  It  is  clothed  on  the 
outside  with  muscles  ;  on  the  inside 
it  is  lined  with  mucous  membrane, 
continuous  with  that  of  the  other  air 
passages. 

The  larynx  has  for  a  framework 
two  cartilages,  the  thyroid  and  the 
cricoid,  one  above  the  other.  The 
larger  of  these,  called  the  thyroid, 
from  a  supposed  resemblance  to  a 
shield,  consists  of  two  extended  wings 
which  join  in  front,  but  are  separated 
by  a  wide  interval  behind.  The  united 
edges  in  front  project  and  form  the 
"  Adam's  apple,"  plainly  seen  and 

easily  felt  On    mOSt   people,  especially     A,hyoidbone;  B,  thyro-hyoid  mem- 
brane;   C,  thyroid  cartilage;    D, 
crico-thyroid  membrane  ;    E,  cri- 
coid cartilage,  lateral    ligaments 
...  1111  seen  on  each  side ;   F,  upper  ring 

horns  which  are  connected  by  bands 
to  the  hyoid  bone,  from  which  the 
larynx  is  suspended.  This  bone  is 
attached  by  muscles  and  ligaments  to  the  skull.  It  lies  at 
the  base  of  the  tongue,  and  can  be  readily  felt  by  the  finger 
behind  the  chin  at  the  angle  of  the  jaw  and  the  neck  (sec.  41 
and  Fig.  46).  From  the  under  side  of  the  thyroid  two  horns 
project  downwards  to  become  jointed  to  the  cricoid.  The 
thyroid  thus  rests  upon,  and  is  movable  on,  the  cricoid  cartilage. 


on  very  lean  men. 

Above  and  from  the  sides  rise  two 


FIG.  148.  — View  of  the  Carti- 
lages and  Ligaments  of  the 
Larynx.  (Anterior  view.) 


of  the  trachea.  ("Adam's  apple  " 
is  in  the  V-shaped  groove  on  a 
line  with  B  and  C.) 


358 


PRACTICAL    PHYSIOLOGY. 


The  cricoid  cartilage,  so  called  from  its  fancied  resemblance 
to  a  signet-ring,  is  smaller  but  thicker  and  stronger  than  the 
thyroid,  and  forms  the  lower  and  back  part  of  the  cavity  of 
the  larynx.  This  cartilage  is  quite  sensitive  to  pressure  from 
the  fingers,  and  is  the  cause  of  the  sharp  pain  felt  when  we 

try  to  swallow  a  large  and  hard  piece 
of  food  not  properly  chewed. 

On  the  upper  edge  of  the  cricoid 
cartilage  are  perched  a  pair  of  very 
singular  cartilages,  pyramidal  in 
shape,  called  the  arytenoid,  which 
are  of  great  importance  in  the  pro- 
duction of  the  voice.  These  carti- 
lages are  capped  with  little  horn-like 
projections,  and  give  attachment  at 
their  anterior  angles  to  the  true 
vocal  cords,  and  at  their  posterior 
angles  to  the  muscles  which  open 
and  close  the  glottis,  or  upper  open- 
ing of  the  windpipe.  When  in  their 
natural  position  the  arytenoid  carti- 
FIG.  149.-  Diagram  of  a  Sectional  lages  resemble  somewhat  the  mouth 

View  of  Nasal  and  Throat  Pas-      r&        .     . 

of  a  pitcher,  hence  their  name. 


sages. 

C,  nasal  cavities;  T,  tongue  ;  L,  lower 
jaw;  M,  mouth;  U,  uvula;  E,  epi- 
glottis ;  G,  larynx;  O,  resophagus. 


351.    The  Vocal    Cords.     The 

mucous  membrane  which  lines  the 
various  cartilages  of  the  larynx  is  thrown  into  several  folds. 
Thus,  one  fold,  the  free  edge  of  which  is  formed  of  a  band  of 
elastic  fibers,  passes  horizontally  outwards  from  each  side 
towards  the  middle  line,  at  the  level  of  the  base  of  the  aryte- 
noid cartilages.  These  folds  are  called  the  true  vocal  cords, 
by  the  movements  of  which  the  voice  is  produced. 

Above  them  are  other  folds  of  mucous  membrane  called  the 
false  vocal  cords,  which  take  no  part  in  the  production  of  the 


THE  THROAT  AND  THE  VOICE. 


359 


voice.  The  arrangement  of  the  true  vocal  cords,  projecting  as 
they  do  towards  the  middle  line,  reduces  to  a  mere  chink  the 
space  between  the  part  of  the  larynx  above  them  and  the  part 
below  them.  This  constriction  of  the  larynx  is  called  the  glottis. 

352.  The  Mechanism  of  the  Voice.  The  mechanism  of 
the  voice  may  be  more  easily  understood  by  a  study  of  Fig.  150. 
We  have  here  the  larynx, .viewed  from  behind,  with  all  the  soft 
parts  in  connection  with  it.  On  looking  down,  the  folds  form- 
ing the  true  vocal  cords  are  seen 
enclosing  a  V-shaped  aperture  (the 
glottis),  the  narrow  part  being  in  front. 

The  form  of  this  aperture  may  be 
changed  by  the  delicately  coordinate 
activities  of  the  muscles  of  the  larynx. 
For  instance,  the  vocal  cords  may  be 
brought  so  closely  together  that  the 
space  becomes  a  mere  slit.  Air  forced 
through  the  slit  will  throw  the  edges 
of  the  folds  into  vibration  and  a  sound 
will  be  produced. 

The  variations  in  the  form  of  the 
opening  will  determine  the  variations 
in  the  sound.  Now,  if  the  various 
muscles  of  the  larynx  be  relaxed,  the 
opening  of  the  glottis  is  wider.  Thus 
the  air  enters  and  leaves  the  larynx 
during  breathing,  without  throwing 
the  cords  into  vibration  enough  to 
produce  any  sound. 

We  may  say  that  the  production  of  the  voice  is  effected  by 
an  arrangement  like  that  of  some  musical  instruments,  the 
sounds  produced  by  the  vibrations  of  the  vocal  cords  being 
modified  by  the  tubes  above  and  below.  All  musical  sounds 


FIG.  150.  — View  of  the  Carti- 
lages and  Ligaments  of  the 
Larynx.  (Posterior  view.) 

A,  epiglottis ;  B,  thyroid  cartilage: 
C,  arytenoid  cartilage;  D,  liga- 
ment connecting  lower  cornu  of 
the  thyroid  with  the  back  of  the 
cricoid  cartilage  ;  E,  cricoid  carti- 
lage ;  F,  upper  ring  of  the  trachea. 


360 


PRACTICAL    PHYSIOLOGY. 


are  due  to  movements  or  vibrations  occurring  with  a  certain 
regularity,  and  they  differ  in  loudness,  pitch,  and  quality. 
Loudness  of  the  sound  depends  upon  the  extent  of  the  vibra- 
tions, pitch  on  the  rapidity  of  the  vibrations,  and  quality  on 
the  admixture  of  tones  produced  by 
vibrations  of  varying  rates  of  rapidity, 
related  to  one  another. 

353.  Factors  in  the  Production  of 
the  Voice.  Muscles  which  pass  from 
the  cricoid  cartilage  to  the  outer  angle 
of  the  arytenoids  act  to  bring  the  vocal 
cords  close  together,  and  parallel  to  one 
another,  so  that  the  space  between  them 
is  narrowed  to  a  slit.  A  strong  expira- 
tion now  drives  the  air  from  the  lungs 
through  the  slit,  between  the  cords,  and 
throws  them  into  vibration.  The  vibra- 
tion is  small  in  amount,  but  very  rapid. 
Other  muscles  are  connected  with  the 
arytenoid  cartilages  which  serve  to  sep- 

FIG.   151.  —  Longitudinal  ..    . 

Section   of   the   Larynx.      arate  the  VOCal  Cords  and  to  °Pen  Wldely 

(Showing  the  vocal  cords.)   the  glottis.     The  force  of  the  outgoing 

A,  epiglottis ;  B,  section  of  hyoid  current  of  air  determines  the  extent  of 

bone;  c,  superior  vocal  cord ;  the  movement  of  the  cords,  and  thus  the 

D,  ventricle  of  the  larynx ;  E, 

inferior  vocal  cord;  F,  section     loudttCSS  of  the  SOUnd  will  increase  with 

of  the  thyroid  cartilage;    H,    greater  force    Qf  expiration. 

section  of  anterior  portion  of 

the  cricoid  cartilage ;  K,  tra-       We  have  just  learned  that  the  pitch 
chea;  L,  section  of  the  poste-  of  sound   depends  on   the   rapidity   of 

nor    portion    of    the    cncoid  ,  .    •     .  . 

cartilage;  M,  arytenoid  carti-  the  Vibrations.       This    depends  Upon  the 

lage;   N ,  section  of  the  aryte-  Jen    th  Qf    the    CQrds  and    their  tightness, 
noid  muscle.  ° 

for  the  shorter  and  tighter  a  string  is, 

the  higher  is  the   note  which  its   vibration   produces.      The 
vocal  cords  of  women  are  about  one-third  shorter  than  those 


THE  THROAT  AND  THE  VOICE.  361 

of  men,  hence  the  higher  pitch  of  the  notes  they  produce. 
In  children  the  vocal  cords  are  shorter  than  in  adults.1  The 
cords  of  tenor  singers  are  also  shorter  than  those  of  basses  and 
baritones.  The  muscles  within  the  larynx,  of  course,  play  a 
very  important  part  in  altering  the  tension  of  the  vocal  cords. 
Those  qualities  of  the  voice  which  we  speak  of  as  sweet,  harsh, 
and  sympathetic  depend  to  a  great  extent  upon  the  peculiar 
structure  of  the  vocal  cords  of  the  individual. 

Besides  the  physical  condition  of  the  vocal  cords,  as  their 
degree  of  smoothness,  elasticity,  thickness,  and  so  on,  other 
factors  determine  the  quality  of  an  individual's  voice.  Thus, 
the  general  shape  and  structure  of  the  trachea,  the  larynx,  the 
throat,  and  mouth  all  influence  the  quality  of  voice.  In  fact, 
the  air  passages,  both  below  and  above  the  vibrating  cords, 
act  as  resonators,  or  resounding  chambers,  and  intensify  and 
modify  the  sounds  produced  by  the  cords.  It  is  this  fact  that 
prompts  skillful  teachers  of  music  and  elocution  to  urge  upon 
their  pupils  the  necessity  of  the  mouth  being  properly  opened 
during  speech,  and  especially  during  singing. 

Experiment  187.  To  show  the  anatomy  of  the  throat.  Study  the  general 
construction  of  the  throat  by  the  help  of  a  hand  mirror.  Repeat  the  same 
on  the  throat  of  some  friend. 

Experiment  188.  To  show  the  construction  of  the  vocal  organs.  Get  a 
butcher  to  furnish  two  windpipes  from  a  sheep  or  a  calf.  They  differ 
somewhat  from  the  vocal  organs  of  the  human  body,  but  will  enable  us  to 
recognize  the  different  parts  which  have  been  described,  and  thus  to  get  a 
good  idea  of  the  gross  anatomy. 

One  specimen  should  be  cut  open  lengthwise  in  the  middle  line  in  front, 
and  the  other  cut  in  the  same  way  from  behind. 

354.  Speech.  Speech  is  to  be  distinguished  from  voice. 
It  may  exist  without  voice,  as  in  a  whisper.  Speech  consists 

1  The  voices  of  boys  "  break,"  or  "  change,"  because  of  the  sudden  growth  or 
enlargement  of  the  larynx,  and  consequent  increase  in  length  of  the  vocal  cords,  at 
from  fourteen  to  sixteen  years  of  age.  No  such  enlargement  takes  place  in  the 
larynxes  of  girls :  therefore  their  voices  undergo  no  such  sudden  change. 


362  PRACTICAL  PHYSIOLOGY. 

of  articulated  sounds,  produced  by  the  action  of  various  parts 
of  the  mouth,  throat,  and  nose.  Voice  is  common  to  most 
animals,  but  speech  is  the  peculiar  privilege  of  man. 

The  organ  of  speech  is  perhaps  the  most  delicate  and  perfect 
motor  apparatus  in  the  whole  body.     It  has  been  calculated 
that  upwards  of  900  movements  per  minute 
can    be   made   by  the    movable   organs   of 
speech  during  reading,  speaking,  and  sing- 
ing.    It  is  said  that  no  less  than  a  hundred 
different  muscles   are  called  into  action  in 
talking.    Each  part  of  this  delicate  apparatus 
is  so  admirably  adjusted  to  every  other  that 
FIG.  152.  — Diagram-   all  parts  of  this  most  complex  machinery 
matic  Horizontal   act  in  perfect  harmony. 

Section  of  Larynx  to          There  ^&  ^^  articulate  sounds    called 
show  the    Direction 

of  Pull  of  the  Pos-   vowel  or  vocal,  from  the  fact  that  they  are 
terior   Crico-Aryte-   produced  by  the  vocal  cords,  and  are   but 

SSJSETvtS  slishtly modified  as  they  pass  out  of  the 

Cords.  (Dotted  lines   mouth.      The  true  vowels,  a,  <?,  i,  oj  u,  can 

show  position  in  ab-  an  be  sounded  alone,  and  may  be  prolonged 

in  expiration.     These  are  the  sounds  chiefly 

used   in    singing.      The    differences   in   their    characters   are 

produced  by  changes  in  the  position  of  the  tongue,  mouth, 

and  lips. 

Consonants  are  sounds  produced  by  interruptions  of  the  out- 
going current  of  air,  but  in  some  cases  have  no  sound  in  them- 
selves, and  serve  merely  to  modify  vowel  sounds.  Thus,  when 
the  interruption  to  the  outgoing  current  takes  place  by  move- 
ments of  the  lips,  we  have  the  labial  consonants,  /,  b,  f,  and  v. 
When  the  tongue,  in  relation  with  the  teeth  or  hard  palate, 
obstructs  the  air,  the  dental  consonants,  d,  t,  /,  and  s  are  pro- 
duced. Gutturals,  such  as  k,  g,  ch,  gh,  and  r,  are  due  to  the 
movements  of  the  root  of  the  tongue  in  connection  with  the 
soft  palate  or  pharynx. 


THE  THROAT  AND  THE  VOICE.  363 

To  secure  an  easy  and  proper  production  of  articulate  sounds, 
the  mouth,  teeth,  lips,  tongue,  and  palate  should  be  in  perfect 
order.  The  modifications  in  articulation  occasioned  by  a  de- 
fect in  the  palate,  or  in  the  uvula,  by  the  loss  of  teeth,  from 
disease,  and  from  congenital  defects,  are  sufficiently  familiar. 
We  have  seen  that  speech  consists  essentially  in  a  modification 
of  the  vocal  sounds  by  the  accessory  organs,  or  by  parts  above 
the  larynx,  the  latter  being  the  essential  vocal  instrument. 

Many  animals  have  the  power  of  making  articulated  sounds ; 
a  few  have  risen,  like  man,  to  the  dignity  of  sentences,  but 
these  are  only  by  imitation  of  the  human  voice.  Both  vowels 
and  consonants  can  be  distinguished  in  the  notes  of  birds,  the 
vocal  powers  of  which  are  generally  higher  than  those  of  mam- 
mals. The  latter,  as  a  rule,  produce  only 
vowels,  though  some  are  also  able  to  form 
consonants. 

Persons  idiotic  from  birth  are  incapable 
of  producing  any  other  vocal  sounds  than 
inarticulate  cries,  although  supplied  with  all 
the  internal  means  of  articulation.  Persons 
deaf  and  dumb  are  in  the  same  situation,  FIG.  153.  —  Direction 
though  from  a  different  cause;  the  one  being  of  Pull  of  the  Lateral 

,  .         »»•.'*•  i    ^i  i         i     •  Crico-Arytenoids, 

incapable  of  imitating,  and  the  other  being      which  adduct  the 
deprived  of  hearing  the  sounds  to  be  imitated.       Vocal  Cords.    (Dot- 
In  whispering,  the  larynx  takes  scarcely      ted  lines  show  POS1" 

,  ,  f     ,  tion  in  adduction.) 

any  part  in  the  production  or  the  sounds  ; 
the  vocal  cords  remain  apart  and  comparatively  slack,  and  the 
expiratory  blast  rushes  through  without  setting  them  in  vibration. 
In  stammering,  spasmodic  contraction  of  the  diaphragm 
interrupts  the  effort  of  expiration.  The  stammerer  has  full 
control  of  the  mechanism  of  articulation,  but  not  of  the  expi- 
ratory blast.  His  larynx  and  his  lips  are  at  his  command,  but 
not  his  diaphragm.  To  conquer  this  defect  he  must  train  his 
muscles  of  respiration  to  calm  and  steady  action  during  speech. 


364  PRACTICAL    PHYSIOLOGY. 

The  stutterer,  on  the  other  hand,  has  full  control  of  the  muscles 
of  expiration.  His  diaphragm  is  well  drilled,  but  his  lips  and 
tongue  are  insubordinate. 

355.  The  Care  of  the  Throat  and  Voice.  The  throat, 
exposed  as  it  is  to  unwholesome  and  overheated  air,  irritating 
dust  of  the  street,  factories,  and  workshops,  is  often  inflamed, 
resulting  in  that  common  ailment,  sore  throat.  The  parts  are 
red,  swollen,  and  quite  painful  on  swallowing.  Speech  is  often 
indistinct,  but  there  is  no  hoarseness  or  cough  unless  the  uvula 
is  lengthened  and  tickles  the  back  part  of  the  tongue.  Slight 
sore  throat  rarely  requires  any  special  treatment,  aside  from 
simple  nursing. 

The  most  frequent  cause  of  throat  trouble  is  the  action  of 
cold  upon  the  heated  body,  especially  during  active  perspira- 
tion. For  this  reason  a  cold  bath  should  not  be  taken  while  a 
person  is  perspiring  freely.  The  muscles  of  the  throat  are 
frequently  overstrained  by  loud  talking,  screaming,  shouting, 
or  by  reading  aloud  too  much.  People  who  strain  or  misuse 
the  voice  often  suffer  from  what  is  called  "  clergyman's  sore 
throat."  Attacks  of  sore  throat  due  to  improper  methods  of 
breathing  and  of  using  the  voice  should  be  treated  by  judicious 
elocutionary  exercises  and  a  system  of  vocal  gymnastics,  under 
the  direction  of  proper  teachers. 

Persons  subject  to  throat  disease  should  take  special  care  to 
wear  suitable  underclothing,  adapted  to  the  changes  of  the 
seasons.  Frequent  baths  are  excellent  tonics  to  the  skin,  and 
serve  indirectly  to  protect  one  liable  to  throat  ailments  from 
changes  in  the  weather.  It  is  not  prudent  to  muffle  the  neck 
in  scarfs,  furs,  and  wraps,  unless  perhaps  during  an  unusual 
exposure  to  cold.  Such  a  dress  for  the  neck  only  makes  the 
parts  tender,  and  increases  the  liability  to  a  sore  throat. 

Every  teacher  of  elocution  or  of  vocal  music,  entrusted  with 
the  training  of  a  voice  of  some  value  to  its  possessor,  should 


THE    THROAT    AND    THE    VOICE.  365 

have  a  good,  practical  knowledge  of  the  mechanism  of  the 
voice.  Good  voices  are  often  injured  by  injudicious  manage- 
ment on  the  part  of  some  incompetent  instructor.  It  is  always 
prudent  to  cease  speaking  or  singing  in  public  the  moment 
there  is  any  hoarseness  or  sore  throat. 

,  The  voice  should  not  be  exercised  just  after  a  full  meal,  for 
a  full  stomach  interferes  with  the  free  play  of  the  diaphragm. 
A  sip  of  water  taken  at  convenient  intervals,  and  held  in  the 
mouth  for  a  moment  or  two,  will  relieve  the  dryness  of  the 
throat  during  the  use  of  the  voice. 

356.  Effect  of  Alcohol  upon  the  Throat  and  Voice.     Alco- 
holic beverages  seriously  injure  the  throat,  and  consequently 
the  voice,  by  causing  a  chronic  inflammation  of  the  membrane 
lining  the  larynx  and  the  vocal  cords.     The  color  is  changed 
from  the  healthful  pink  to  red,  and  the  natural  smooth  surface 
becomes  roughened  and  swollen,  and  secretes  a  tough  phlegm. 

The  vocal  cords  usually  suffer  from  this  condition.  They 
are  thickened,  roughened,  and  enfeebled,  the  delicate  vibration 
of  the  cords  is  impaired,  the  clearness  and  purity  of  the  vocal 
tones  are  gone,  and  instead  the  voice  has  become  rough  and 
husky.  So  well  known  is  this  result  that  vocalists,  whose 
fortune  is  the  purity  and  compass  of  their  tones,  are  scrupu- 
lously careful  not  to  impair  these  fine  qualities  by  convivial 
indulgences. 

357.  Effect  of  Tobacco  upon  the  Throat  and  Voice.     The 

effect  of  tobacco  is  often  specially  serious  upon  the  throat,  pro- 
ducing a  disease  well  known  to  physicians  as  "  the  smoker's 
sore  throat."  Still  further,  it  produces  inflammation  of  the 
larynx,  and  thus  entails  disorders  of  the  vocal  cords,  involving 
rough  voice  and  harsh  tones.  For  this  reason  vocalists  rarely 
allow  themselves  to  come  under  the  narcotic  influence  of 
tobacco  smoke.  It  is  stated  that  habitual  smokers  rarely  have 
a  normal  condition  of  the  throat. 


366  PRACTICAL    PHYSIOLOGY. 


ADDITIONAL  EXPERIMENTS. 

Experiment  189.  To  illustrate  the  importance  of  the  resonating  cavity 
of  the  nose  in  articulation.  Pinch  the  nostrils,  and  try  to  pronounce  slowly 
the  words  "  Lincoln,"  "  something,"  or  any  other  words  which  require  the 
sound  of  m,  In,  or  ng. 

Experiment  190.     To  illustrate  the  passage  of  air  through  the  glottis. 
Take  two  strips  of  India  rubber,  and  stretch  them  over  the  open  end  of  a 
boy's  "bean-blower,"  or  any  kind  of  a  tube.     Tie  them  tightly 
with  thread,  so  that  a  chink  will  be  left  between  them,  as  shown 
in  Fig.  1 54. 

Force  the  air  through  such  a  tube  by  blowing  hard,  and  if 
the  strips  are  not  too  far  apart  a  sound  will  be  produced.  The 
sound  will  vary  in  character,  just  as  the  bands  are  made  tight 
or  loose. 

Experiment  191.     "A  very  good  illustration  of  the  action  of 
the  vocal  bands  in  the  production  of  the  voice  may  be  given  by 
FIG  i<u      means  °f  a  piece  of  bamboo  or  any  hollow  wooden  tube,  and  a 
strip  of  rubber,  about  an  inch  or  an  inch  and  a  half  wide,  cut 
from  the  pure  sheet  rubber  used  by  dentists. 

"  One  end  of  the  tube  is  to  be  cut  sloping  in  two  directions,  and  the  strip 
of  sheet  rubber  is  then  to  be  wrapped  round  the  tube,  so  as  to  leave  a  nar- 
row slit  terminating  at  the  upper  corners  of  the  tube. 

"  By  blowing  into  the  other  end  of  the  tube  the  edges  of  the  rubber 
bands  will  be  set  in  vibration,  and  by  touching  the  vibrating  membrane  at 
different  points  so  as  to  check  its  movements  it  may  be  shown  that  the 
pitch  of  the  note  emitted  depends  upon  the  length  and  breadth  of  the 
vibrating  portion  of  the  vocal  bands.  "  *  —  DR.  H.  P.  BOWDITCH. 

1  This  experiment  and  several  others  in  this  book,  are  taken  from  Professor 
Bowditch's  little  book  called  Hints  for  Teachers  of  Physiology,  a  work  which 
should  be  mastered  by  every  teacher  of  physiology  in  higher  schools. 

NOTE.  The  limitations  of  a  text-book  on  physiology  for  schools  do  not  permit 
so  full  a  description  of  the  voice  as  the  subject  deserves.  For  additional  details,  the 
student  is  referred  to  Cohen's  The  Throat  and  the  Voice,  a  volume  in  the  "  Ameri. 
can  Health  Primer  Series."  Price  40  cents. 


CHAPTER   XIII. 

ACCIDENTS    AND    EMERGENCIES. 

358.  Prompt  Aid  to  the  Injured.  A  large  proportion  of 
the  accidents,  emergencies,  and  sudden  sicknesses  that  happen 
do  not  call  for  medical  or  surgical  attention.  For  those  that  do 
require  the  services  of  a  physician  or  surgeon,  much  can  be 
often  done  before  the  arrival  of  professional  help.  Many  a 
life  has  been  saved  and  much  suffering  and  anxiety  prevented 
by  the  prompt  and  efficient  help  of  some  person  with  a  cool 
head,  a  steady  hand,  and  a  practical  knowledge  of  what  to  do 
first.  Many  of  us  can  recall  with  mingled  admiration  and  grati- 
tude the  prompt  services  rendered  our  families  by  some  neigh- 
bor or  friend  in  the  presence  of  an  emergency  or  sudden  illness. 

In  fact,  what  we  have  studied  in  the  preceding  chapters 
becomes  tenfold  more  interesting,  instructive,  and  of  value  to 
us,  if  we  are  able  to  supplement  such  study  with  its  practical 
application  to  the  treatment  of  the  more  common  and  less  seri- 
ous accidents  and  emergencies. 

While  no  book  can  teach  one  to  have  presence  of  mind,  a 
cool  head,  or  to  restrain  a  more  or  less  excitable  temperament 
in  the  midst  of  sudden  danger,  yet  assuredly  with  proper  knowl- 
edge for  a  foundation,  a  certain  self-confidence  may  be  acquired 
which  will  do  much  to  prevent  hasty  action,  and  to  maintain  a 
useful  amount  of  self-control. 

Space  allows  us  to  describe  briefly  in  this  chapter  only  a  few 
of  the  simplest  helps  in  the  more  common  accidents  and  emer- 
gencies which  are  met  with  in  everyday  life.1 

1  The  teacher  or  student  who  is  disposed  to  study  the  subject  more  thor- 
oughly and  in  more  detail  than  is  possible  in  a  class  text-book,  will  find  all  that  is 
needed  in  the  following  excellent  books,  which  are  readily  obtained  by  purchase,  or 


368 


PRACTICAL    PHYSIOLOGY. 


359.  Hints  as  to  what  to  Do  First.     Retain  so  far  as  pos- 
sible  your  presence   of   mind,  or,  in   other  words,  keep  cool. 
This  is  an  all-important  direction.     Act  promptly  and  quietly, 
but   not   with   haste.     Whatever  you   do,  do   in   earnest;   and 
never  act  in  a  half-hearted  manner  in  the  presence  of  danger. 
Of  course,  a  knowledge  of  what  to  do  and  how  to  do  it  will 
contribute  much  towards  that  self-control  and  confidence  that 
command  success.     Be  sure  and  send  for  a  doctor  at  once  if 

the  emergency  calls  for  skilled 
service.  All  that  is  expected  of 
you  under  such  circumstances  is  to 
tide  over  matters  until  the  doctor 
comes. 

Do  not  presume  upon  any  smat- 
tering of  knowledge  you  have,  to 
assume  any  risk  that  might  lead  to 
serious  results.  Make  the  sufferer 
comfortable  by  giving  him  an  abun- 
dance of  fresh  air  and  placing  him 
in  a  restful  position.  Do  all  that  is 
possible  to  keep  back  the  crowd  of 
FIG.  155- -Showing  how  Digital  curious  lookers-on,  whom  a  morbid 

Compression  should  be  applied 

to  the  Brachial  Artery.  curiosity    has   gathered    about   the 

injured    person.      Loosen   all   tight 

articles  of  clothing,  as  belts,  collars,  corsets,  and  elastics. 
Avoid  the  use  of  alcoholic  liquors.  They  are  rarely  of  any 
real  service,  and  in  many  instances,  as  in  bleeding,  may  do 
much  harm. 

360.  Incised  and  Lacerated  Wounds.     An  incised  or  cut 
wound  is  one  made  by  a  sharp  instrument,  as  when  the  finger 

may  be  found  in  the  public  libraries  of  larger  towns  :  Dulles'  Accidents  and  Emer- 
gencies ;  Pilcher's  First  Aid  in  Illness  and  Injury ;  Doty's  Prompt  Aid  to  the 
Injured ;  and  Johnston's  "  Surgical  Injuries  and  Surgical  Diseases,"  a  special  article 
in  Roosevelt's  In  Sickness  and  in  Health. 


ACCIDENTS    AND    EMERGENCIES.  369 

is  cut  with  a  knife.  Such  a  wound  bleeds  freely  because  the 
clean-cut  edges  do  not  favor  the  clotting  of  blood.  In  slight 
cuts  the  bleeding  readily  ceases,  and  the  wound  heals  by  pri- 
mary union,  or  by  "  first  intention,"  as  surgeons  call  it. 

Lacerated  and  contused  wounds  are  made  by  a  tearing  or 
bruising  instrument,  for  example,  catching  the  finger  on  a  nail. 
Such  wounds  bleed  but  little,  and  the  edges  and  surfaces  are 
rough  and  ragged. 

If  the  incised  wound  is  deep  or  extensive,  a  physician  is 
necessary  to  bring  the  cut  edges  together  by  stitches  in  order 
to  get  primary  union.  Oftentimes,  in  severe  cuts,  and  generally 
in  lacerations,  there  is  a  loss  of  tissue,  so  that  the  wound  heals 
by  "  second  intention  "  ;  that  is,  the  wound  heals  from  the 
bottom  by  a  deposit  of  new  cells  called  granulations,  which 
gradually  fill  it  up.  The  skin  begins  to  grow  from  the  edges 
to  the  center,  covering  the  new  tissue  and  leaving  a  cicatrix 
or  scar  with  which  every  one  is  familiar. 

361.  Contusion  and  Bruises.  An  injury  to  the  soft  tissues, 
caused  by  a  blow  from  some  blunt  instrument,  or  a  fall,  is  a 
contusion,  or  bruise.  It  is  more  or  less  painful,  followed  by 
discoloration  due  to  the  escape  of  blood  under  the  skin,  which 
often  may  not  be  torn  through.  A  black  eye,  a  knee  injured 
by  a  fall  from  a  bicycle,  and  a  finger  hurt  by  a  baseball,  are 
familiar  examples  of  this  sort  of  injury.  Such  injuries  ordi- 
narily require  very  simple  treatment. 

The  blood  which  has  escaped  from  the  capillaries  is  slowly 
absorbed,  changing  color  in  the  process,  from  blue  black  to 
green,  and  fading  into  a  light  yellow.  Wring  out  old  towels  or 
pieces  of  flannel  in  hot  water,  and  apply  to  the  parts,  changing 
as  they  become  cool.  For  cold  applications,  cloths  wet  with 
equal  parts  of  water  and  alcohol,  vinegar,  and  witch-hazel  may 
be  used.  Even  if  the  injury  is  apparently  slight  it  is  always 
safe  to  rest  the  parts  for  a  few  days. 


370 


PRACTICAL    PHYSIOLOGY. 


When  wounds  are  made  with  ragged  edges,  such  as  those 
made  by  broken  glass  and  splinters,  more  skill  is  called  for. 
Remove  every  bit  of  foreign  substance.  Wash  the  parts 
clean  with  one  of  the  many  antiseptic  solutions,  bring  the  torn 
edges  together,  and  hold  them  in  place  with  strips  of  plaster. 
Do  not  cover  such  an  injury  all  over  with  plaster,  but  leave 
room  for  the  escape  of  the  wound  discharges.  For  an  outside 
£^^^  dressing,  use  compresses  made  of 

J^\  clean   cheese-cloth  or  strips  of   any 

clean  linen  cloth.  The  antiseptic 
corrosive-sublimate  gauze  on  sale  at 
any  drug  store  should  be  used  if  it 
can  be  had. 

Wounds  made  by  toy  pistols,  per- 
cussion-caps, and  rusty  nails  and 
tools,  if  neglected,  often  lead  to 
serious  results  from  blood-poisoning. 
A  hot  flaxseed  poultice  may  be  needed 
for  several  days.  Keep  such  wounds 
clean  by  washing  or  syringing  them 
twice  a  day  with  hot  antiseptics,  which 
are  poisons  to  bacteria  and  kill  them 

Bacteria 

are  widely  distributed,  and  hence  the 
utmost  care  should  be  taken  to  have 
everything  which  is  to  come  in  contact  with  a  wounded  surface 
free  from  the  germs  of  inflammation.  In  brief,  such  injuries 
must  be. kept  scrupulously  neat  and  surgically  clean. 

The  injured  parts  should  be  kept  at  rest.  Movement  and 
disturbance  hinder  the  healing  process. 

362.  Bites  of  Mad  Dogs.  Remove  the  clothing  at  once,  if 
only  from  the  bitten  part,  and  apply  a  temporary  ligature  above 
the  wound.  This  interrupts  the  activity  of  the  circulation  of 


FIG.  1 56.— Dotted  Line  showing  Or   prevent   their  growth. 

the    Course  of    the    Brachial 
Artery. 


ACCIDENTS    AND    EMERGENCIES. 

the  part,  and  to  that  extent  delays  the  absorption  of  the  poison- 
ous saliva  by  the  blood-vessels  of  the  wound.  A  dog  bite  is 
really  a  lacerated  and  contused  wound,  and  lying  in  the  little 
roughnesses,  and  between  the  shreds,  is  the  poisonous  saliva. 
If  by  any  means  these  projections  and  depressions  affordingthe 
lodgment  can  be  removed,  the  poison  cannot  do  much  harm.  If 
done  with  a  knife,  the  wound  would  be  converted,  practically, 
into  an  incised  wound,  and  would  require  treatment  for  such. 

If  a  surgeon  is  at  hand  he  would  probably  cut  out  the  injured 
portion,  or  cauterize  it  thoroughly.  Professional  aid  is  not 
always  at  our  command,  and  in  such  a  case  it  would  be  well 
to  take  a  poker,  or  other  suitable  piece  of  iron,  heat  it  red  hot 
in  the  fire,  wipe  off  and  destroy  the  entire  surface  of  the  wound. 
As  fast  as  destroyed,  the  tissue  becomes  white.  An  iron,  even 
at  a  white  heat,  gives  less  pain  and  at  once  destroys  the  vitality 
of  the  part  with  which  it  comes  in  contact. 

If  the  wound  is  at  once  well  wiped  out,  and  a  stick  of  solid 
nitrate  of  silver  (lunar  caustic)  rapidly  applied  to  the  entire 
surface  of  the  wound,  little  danger  is  to  be  apprehended. 
Poultices  and  warm  fomentations  should  be  applied  to  the 
injury  to  hasten  the  sloughing  away  of  the  part  whose  vitality 
has  been  intentionally  destroyed. 

Any  dog,  after  having  bitten  a  person,  is  apt,  under  a  mis- 
taken belief,  to  be  at  once  killed.  This  should  not  be  done. 
There  is  no  more  danger  from  a  dog-bite,  unless  the  dog  is 
suffering  from  the  disease  called  rabies  or  is  "mad,"  than  from 
any  other  lacerated  wound.  The  suspected  animal  should  be 
at  once  placed  in  confinement  and  watched,  under  proper 
safeguards,  for  the  appearance  of  any  symptoms  that  indicate 
rabies. 

Should  no  pronounced  symptoms  indicate  this  disease  in  the 
dog,  a  great  deal  of  unnecessary  mental  distress  and  worry 
can  be  saved  both  on  the  part  of  the  person  bitten  and  his 
friends. 


372 


PRACTICAL    PHYSIOLOGY. 


363.  Injuries  to  the  Blood-vessels.  It  is  very  important  to 
know  the  difference  between  the  bleeding  from  an  artery  and 
that  from  a  vein. 

If  an  artery  bleeds,  the  blood  leaps  in  spurts,  and  is  of  a 
bright  scarlet  color. 

If  a  vein  bleeds,  the  blood  flows  in  a  steady  stream,  and  is 
of  a  dark  purple  color. 

If  the  capillaries  are  injured  the  blood  merely  oozes. 
Bleeding  from  an  artery  is  a  dangerous  matter  in  proportion 
to  the  size  of  the  vessel,  and  life  itself  may  be  speedily  lost. 

Hemorrhage  from  a  vein  or 
from  the  capillaries  is  rarely 
troublesome,  and  is  ordinarily 
easily  checked,  aided,  if  need 
be,  by  hot  water,  deep  pres- 
sure, the  application  of  some 
form  of  iron  styptic,  or  even 
powdered  alum.  When  an 
artery  is  bleeding,  always  re- 
member to  make  deep  pres- 
sure between  the  wound  and 
the  heart.  In  all  such  cases 
send  at  once  for  the  doctor. 

Do  not  be  afraiol  to  act  at 
once.  A  resolute  grip  in  the 
right  place  with  firm  fingers 
will  do  well  enough,  until  a  twisted  handkerchief,  stout  cord, 
shoestring,  suspender,  or  an  improvised  tourniquet1  is  ready 

1  "  A  tourniquet  is  a.bandage,  handkerchief,  or  strap  of  webbing,  into  the  middle 
of  which  a  stone,  a  potato,  a  small  block  of  wood,  or  any  hard,  smooth  body  is  tied. 
The  band  is  tied  loosely  about  the  limb,  the  hard  body  is  held  over  the  artery  to  be 
constricted,  and  a  stick  is  inserted  beneath  the  band  on  the  opposite  side  of  the  limb 
and  used  to  twist  the  band  in  such  a  way  that  the  limb  is  tightly  constricted  thereby, 
and  the  hard  body  thus  made  to  compress  the  artery  (Fig.  160). 

"  The  entire  circumference  of  the  limb  may  be  constricted  by  any  sort  of  elastic 


FIG.  157.  —  Showing  how  Digital  Com- 
pression should  be  applied  to  the  Fem- 
oral Artery. 


ACCIDENTS    AND    EMERGENCIES.  373 

to  take  its  place.  If  the  flow  of  blood  does  not  stop,  change 
the  pressure  until  the  right  spot  is  found. 

Sometimes  it  will  do  to  seize  a  handful  of  dry  earth  and  crowd 
it  down  into  the  bleeding  wound,  with  a  firm  pressure.  Strips 
of  an  old  handkerchief,  underclothing,  or  cotton  wadding  may 
also  be  used  as  a  compress,  provided  pressure  is  not  neglected. 

In  the  after-treatment  it  is  of  great  importance  that  the 
wound  and  the  dressing  should  be  kept  free  from  bacteria  by 
keeping  everything  surgically  clean. 

364.  Where  and  how  to  Apply  Pressure.  The  principal 
places  in  which  to  apply  pressure  when  arteries  are  injured  and 
bleeding  should  always  be  kept  in  mind. 

Experiment  192.  How  to  tie  a  square  knot.  If  the  student  would  render 
efficient  help  in  accidents  and  emergencies,  to  say  nothing  of  service  on 
scores  of  other  occasions,  he  must  learn  how  to 
tie  a  square  or  "  reef  "  knot.  This  knot  is  secure 
and  does  not  slip  as  does  the  "  granny  "  knot. 
The  square  knot  is  the  one  used  by  surgeons  in 
ligating  vessels  and  securing  bandages.  Unless 
one  knew  the  difference,  the  insecure  "  granny  " 
knot  might  be  substituted. 

A  square  knot  is  tied  by  holding  an  end  of  a 
bandage  or  cord  in  each  hand,  and  then  passing  FlG  158>_showing  how~a 
the  end  in  the  right  hand  over  the  one  in  the  Square  Knot  may  be  tied 
left  and  tying ;  the  end  now  in  the  left  hand  is  with  a  Cord  and  a  Hand- 
passed  over  the  one  in  the  right  and  again  tied.  kerchief. 

If  in  the  finger,  grasp  it  with  the  thumb  and  forefinger,  and 
pinch  it  firmly  on  each  side  ;  if  in  the  hand,  press  on  the 
bleeding  spot,  or  press  with  the  thumb  just  above  and  in  front 
of  the  wrist. 

band  or  rubber  tube,  or  any  other  strong  elastic  material  passed  around  the  limb 
several  times  on  a  stretch,  drawn  tight  and  tied  in  a  knot.  In  this  way,  bleeding  may 
be  stopped  at  once  from  the  largest  arteries.  The  longer  and  softer  the  tube  the 
better.  It  requires  no  skill  and  but  little  knowledge  of  anatomy  to  apply  it  effi- 
ciently,"—  ALEXANDER  B.JOHNSON,  Surgeon  to  Roosevelt  Hospital,  New  York  City 


374  PRACTICAL  PHYSIOLOGY. 

For  injuries  below  the  elbow,  grasp  the  upper  part  of  the 
arm  with  the  hands,  and  squeeze  hard.  The  main  artery  runs 
in  the  middle  line  of  the  bend  of  the  elbow.  Tie  the  knotted  cord 
here,  and  bend  the  forearm  so  as  to  press  hard  against  the  knot. 

For  the  upper  arm,  press  with  the  fingers  against  the  bone 
on  the  inner  side,  and  just  on  the  edge  of  the  swell  of  the 
biceps  muscle.  Now  we  are  ready  for  the  knotted  cord.  Take 
a  stout  stick  of  wood,  about  a  foot  long,  and  twist  the  cord  hard 
with  it,  bringing  the  knot  firmly  over  the  artery. 

For  the  foot  or  leg,  pressure  as  before,  in  the  hollow  behind 
the  knee,  just  above  the  calf  of  the  leg.  Bend  the  thigh  towards 
the  abdomen  and  bring  the  leg  up  against  the  thigh,  with  the 
knot  in  the  bend  of  the  knee. 

365.  Bleeding  from  the  Stomach  and  Lungs.     Blood  that 
comes  from  the  lungs  is  bright  red,  frothy,  or  "soapy."     There 
is  rarely  much  ;   it  usually  follows  coughing,  feels  warm,  and 
has  a  salty  taste.     This  is  a  grave  symptom.     Perfect  rest  on 
the  back  in  bed  and  quiet  must  be  insisted  upon.     Bits  of  ice 
should  be  eaten  freely.    Loosen  the  clothing,  keep  the  shoulders 
well  raised,  and  the  body  in  a  reclining  position  and  absolutely 
at  rest.     Do  not  give  alcoholic  drinks. 

Blood  from  the  stomach  is  not  frothy,  has  a  sour  taste,  and 
is  usually  dark  colored,  looking  somewhat  like  coffee  grounds. 
It  is  more  in  quantity  than  from  the  lungs,  and  is  apt  to  be 
mixed  with  food.  Employ  the  same  treatment,  except  that  the 
person  should  be  kept  flat  on  the  back. 

366.  Bleeding  from  the  Nose.     This  is  the  most  frequent 
and  the  least  dangerous  of  the  various  forms  of  bleeding.     Let 
the  patient  sit  upright ;  leaning  forward  with  the  head  low  only 
increases  the  hemorrhage.     Raise  the  arm  on  the  bleeding 
side ;  do  not  blow  the  nose.     Wring  two  towels  out  of  cold 
water  ;  wrap  one  around  the  neck  and  the  other  properly  folded 
over  the  forehead  and  upper  part  of   the  nose. 


ACCIDENTS    AND    EMERGENCIES. 


375 


Add  a  teaspoonful  of  powdered  alum  to  a  cup  of  water,  and 
snuff  it  up  from  the  hand.  If  necessary,  soak  in  alum  water  a 
piece  of  absorbent  cotton,  which  has  been  wound  around  the 
pointed  end  of  a  pencil  or  penholder  ;  plug  the  nostril  by 
pushing  it  up  with  a  twisting  motion  until  firmly  lodged. 

367.  Burns  or  Scalds.  Burns  or  scalds  are  dangerous  in 
proportion  to  their  extent  and  depth.  A  child  may  have  one 
of  his  fingers  burned  off  with  less 
danger  to  life  than  an  extensive  scald 
of  his  back  and  legs.  A  deep  or  ex- 
tensive burn  or  scald  should  always 
have  prompt  medical  attendance. 

In  burns  by  acids,  bathe  the  parts 
with  an  alkaline  fluid,  as  diluted  am- 
monia, or  strong  soda  in  solution,  and 
afterwards  dress  the  burn. 

In  burns  caused  by  lime,  caustic 
potash,  and  other  alkalies,  soak  the 
parts  with  vinegar  diluted  with  water; 
lemon  juice,  or  any  other  diluted  acid. 

Remove  the  clothing  with  the  great- 
est care.  Do  not  pull,  but  carefully 
cut  and  coax  the  clothes  away  from 
the  burned  places.  Save  the  skin  un- 
broken if  possible,  taking  care  not  to 
break  the  blisters.  The  secret  of 
treatment  is  to  prevent  friction,  and  to  keep  out  the  air.  If 
the  burn  is  slight,  put  on  strips  of  soft  linen  soaked  in  a 
strong  solution  of  baking-soda  and  water,  one  heaping  table- 
spoonful  to  a  cupful  of  water.  This  is  especially  good  for  scalds. 

Carron  oil  is  one  of  the  best  applications.  It  is  simply  half 
linseed-oil  and  half  lime-water  shaken  together.  A  few  table- 
spoonfuls  of  carbolic  acid  solution  to  one  pint  may  be  added 


FIG.  159.  —  Dotted  Line  show- 
ing the  Course  of  the  Fem- 
oral Artery. 


376 


PRACTICAL    PHYSIOLOGY. 


to  this  mixture  to  help  deaden  the  pain.  Soak  strips  of  old 
linen  or  absorbent  cotton  in  this  time-honored  remedy,  and 
gently  apply. 

If  carbolized  or  even  plain  vaseline  is  at  hand,  spread  it 
freely  on  strips  of  old  linen,  and  cover  well  the  burnt  parts, 
keeping  out  the  air  with  other  strips  carefully  laid  on.  Simple 

cold  water  is  better  than 
flour,  starch,  toilet  pow- 
der, cotton  batting,  and 
other  things  which  are 
apt  to  stick,  and  make 
an  after-examination 
very  painful. 

368.    Frost    Bites. 

The  ears,  toes,  nose,  and 
fingers  are  occasionally 
frozen,  or  frost-bitten. 
No  warm  air,  warm 
water,  or  fire  should  be 
allowed  near  the  frozen 
parts  until  the  natural 
temperature  is  nearly  re- 
stored. Rub  the  frozen 
part  vigorously  with  snow 
or  snow-water  in  a  cold 
room.  Continue  this  until  a  burning,  tingling  pain  is  felt, 
when  all  active  treatment  should  cease. 

Pain  shows  that  warmth  and  circulation  are  beginning  to 
return.  The  after  effects  of  a  frost  bite  are  precisely  like  those 
of  a  burn,  and  require  similar  treatment.  Poultices  made  from 
scraped  raw  potatoes  afford  much  comfort  for  an  after  treatment. 

369.  Catching  the  Clothing  on  Fire.  When  the  clothing 
catches  fire,  throw  the  person  down  on  the  ground  or  floor,  as 


FIG.  160.  —  Showing  how  Hemorrhage  from  the 
Femoral  Artery  may  be  arrested  by  the  Use  of 
an  Improvised  Apparatus  (technically  called  a 
Tourniquet}. 


ACCIDENTS    AND    EMERGENCIES.  3/7 

the  flames  will  tend  less  to  rise  toward  the  mouth  and  nostrils. 
Then  without  a  moment's  delay,  roll  the  person  in  a  carpet 
or  hearth-rug,  so  as  to  stifle  the  flames,  leaving  only  the  head 
out  for  breathing. 

If  no  carpet  or  rug  can  be  had,  then  take  off  your  coat,  shawl, 
or  cloak  and  use  it  instead.  Keep  the  flame  as  much  as  possi- 
ble from  the  face,  so  as  to  prevent  the  entrance  of  the  hot  air 
into  the  lungs.  This  can  be  done  by  beginning  at  the  neck 
and  shoulders  with  the  wrapping. 

370.  Foreign  Bodies  in  the  Throat.     Bits  of  food  or  other 
small  objects  sometimes  get  lodged  in  the  throat,  and  are  easily 
extracted  by  the  forefinger,   by  sharp  slaps  on  the  back,  or 
expelled  by  vomiting.     If  it  is  a  sliver  from  a  toothpick,  match, 
or  fishbone,  it  is  no  easy  matter  to  remove  it  ;  for  it  generally 
sticks  into  the  lining  of  the  passage.     If  the  object  has  actually 
passed  into  the  windpipe,  and  is  followed  by  sudden  fits  of 
spasmodic  coughing,  with  a  dusky  hue  to  the  face  and  fingers, 
surgical  help  must  be  called  without  delay. 

If  a  foreign  body,  like  coins,  pencils,  keys,  fruit-stones,  etc., 
is  swallowed,  it  is  not  wise  to  give  a  physic.  Give  plenty  of 
hard-boiled  eggs,  cheese,  and  crackers,  so  that  the  intruding 
substance  may  be  enfolded  in  a  mass  of  solid  food  and  allowed 
to  pass  off  in  the  natural  way. 

371.  Foreign  Bodies  in  the  Nose.     Children  are   apt   to 
push  beans,  peas,  fruit-stones,  buttons,  and  other  small  objects, 
into  the  nose.      Sometimes  we  can  get  the  child  to  help  by 
blowing  the  nose  hard.     At  other  times,  a  sharp  blow  between 
the  shoulders  will  cause  the  substance  to  fall  out.     If  it  is  a 
pea  or  bean,  which  is  apt  to  swell  with  the  warmth  and  mois- 
ture, call  in  medical  help  at  once. 

372.  Foreign  Bodies  in  the  Ear.     It  is  a  much  more  diffi- 
cult matter  to  get  foreign  bodies  out  of  the  ear  than  from  the 


PRACTICAL    PHYSIOLOGY. 

nose.  Syringe  in  a  little  warm  water,  which  will  often  wash 
out  the  substance.  If  live  insects  get  into  the  ear,  drop  in  a 
little  sweet  oil,  melted  vaseline,  salt  and  water,  or  even  warm 
molasses. 

If  the  tip  of  the  ear  is  pulled  up  gently,  the  liquid  will  flow 
in  more  readily.  If  a  light  is  held  close  to  the  outside  ear,  the 
insect  may  be  coaxed  to  crawl  out  towards  the  outer  opening 
of  the  ear,  being  attracted  by  the  bright  flame. 

373.  Foreign  Bodies  in  the  Eye.  Cinders,  particles  of 
dust,  and  other  small  substances,  often  get  into  the  eye,  and 
cause  much  pain.  It  will  only  make  bad  matters  worse  to  rub 


FIG.  161.  —  Showing  how  the  Upper  Eyelid  may  be  everted  with  a 
Pencil  or  Penholder. 

the  eye.  Often  the  copious  flow  of  tears  will  wash  the  sub- 
stance away.  It  is  sometimes  seen,  and  removed  simply  by 
the  twisted  corner  of  a  handkerchief  carefully  used.  If  it  is 
not  removed,  or  even  found,  in  this  way,  the  upper  lid  must  be 
turned  back. 

This  is  done  usually  as  follows :  Seize  the  lashes  between 
the  thumb  and  forefinger,  and  draw  the  edge  of  the  lid  away 
from  the  eyeball.  Now,  telling  the  patient  to  look  down,  press 
a  slender  lead-pencil  or  penholder  against  the  lid,  parallel  to 
and  above  the  edge,  and  then  pull  the  edge  up,  and  turn  it  over 
the  pencil  by  means  of  the  lashes. 


ACCIDENTS    AND    EMERGENCIES. 


379 


The  eye  is  now  readily  examined,  and  usually  the  foreign 
body  is  easily  seen  and  removed.  Do  not  increase  the  trouble 
by  rubbing  the  eye  after  you 
fail,  but  get  at  once  skilled 
help.  After  the  substance  has 
been  removed,  bathe  the  eye 
for  a  time  with  hot  water. 

If  lime  gets  into  the  eye,  it  may  do  a 
great  amount  of  mischief,  and  generally 
requires  medical  advice,  or  permanent 
injury  will  result.  Until  such  advice 
can  be  had,  bathe  the  injured  parts 
freely  with  a  weak  solution  of  vinegar 
and  hot  water. 

374.  Broken  Bones.  Loss  of  power, 
pain,  and  swelling  are  symptoms  of  a 
broken  bone  that  may  be  easily  recog- 
nized. Broken  limbs  should  always  be 
handled  with  great  care  and  tenderness. 
If  the  accident  happens  in  the  woods, 
the  limb  should  be  bound  with  hand- 
kerchiefs, suspenders,  or  strips  of  cloth- 
ing, to  a  piece  of  board,  pasteboard,  or 
bark,  padded  with  moss  or  grass,  which 
will  do  well  enough  for  a  temporary 
splint.  Always  put  a  broken  arm  into 
a  sling  after  the  splints  are  on. 

Never  move  the  injured  person  until 
the  limb  is  made  safe  from  further  in- 
juries by  putting  on  temporary  splints. 
If  you  do  not  need  to  move  the  person,  FlG>  ^L-  Showing  how 

an  Umbrella  may  be  used 

keep  the  limb  in  a  natural,  easy  position,       as  a  Temporary  Splint  in 

Until  the  doctor  COmeS.  Fracture  of  the  Leg. 


3  So 


PRACTICAL    PHYSIOLOGY. 


Remember  that  this  treatment  for  broken  bones  is  only  to 
enable  the  patient  to  be  moved  without  further  injury.  A 
surgeon  is  needed  at  once  to  set  the  broken  bone. 

375.  Fainting.    A  fainting  person  should  be  laid  flat  at  once. 
Give  plenty  of  fresh  air,  and  dash  cold  water,  if  necessary,  on 
the  head  and  neck.      Loosen  all  tight 
clothing.     Smelling-salts  may  be  held  to 
the  nose,  to  excite  the  nerves  of  sensation. 

376.  Epileptic  and  Hysterical  Fits, 
Convulsions  of  Children.  Sufferers 
from  "  fits  "  are  more  or  less  common. 
In  epilepsy,  the  sufferer  falls  with  a 
peculiar  cry ;  a  loss  of  consciousness,  a 
moment  of  rigidity,  and  violent  convul- 
sions follow.  There  is  foaming  at  the 
mouth,  the  eyes  are  rolled  up,  and  the 
tongue  or  lips  are  often  bitten.  When 
the  fit  is  over  the  patient  remains  in  a 
dazed,  stupid  state  for  some  time.  It  is 
a  mistake  to  struggle  with  such  patients, 

FIG.  162.  — Showing  how  a     or   to   hold   tnem   down   and   keeP   them 

quiet.     It  does  more  harm  than  good. 
See  that  the  person  does  not  injure 

himself  ;  crowd  a  pad  made  from  a  folded 
handkerchief  or  towel  between  the  teeth,  to  prevent  biting  of 
the  lips  or  tongue.  Do  not  try  to  make  the  sufferer  swallow 
any  drink.  Unfasten  the  clothes,  especially  about  the  neck 
and  chest.  Persons  who  are  subject  to  such  fits  should  rarely 
go  out  alone,  and  never  into  crowded  or  excited  gatherings  of 
any  kind. 

Hysterical  fits  almost  always  occur  in  young  women.  Such 
patients  never  bite  their  tongue  nor  hurt  themselves.  Placing 
a  towel  wrung  out  in  cold  water  across  the  face,  or  dashing  a 


Pillow  may  be  used  as 
a  Temporary  Splint  in 
Fracture  of  the  Leg. 


ACCIDENTS    AND    EMERGENCIES.  381 

little  cold  water  on  the  face  or  neck,  will  usually  cut  short  the 
fit,  speaking  firmly  to  the  patient  at  the  same  time.  Never 
sympathize  too  much  with  such  patients  ;  it  will  only  make 
them  a  great  deal  worse. 

377.  Asphyxia.     Asphyxia  is  from  the  Greek,  and  means 
an  "  absence  of  pulse."     This  states  a  fact,  but  not  the  cause. 
The  word  is  now  commonly  used  to  mean  suspended  anima- 
tion.    When  for  any  reason  the    proper   supply  of  oxygen  is 
cut  off,  the  tissues  rapidly  load  up  with  carbon  dioxid.     The 
blood  turns  dark,  and  does  not  circulate.     The  healthy  red  or 
pink  look  of  the  lips  and  finger-nails  becomes  a  dusky  purple. 
The  person  is  suffering  from  a  lack  of  oxygen ;  that  is,  from 
asphyxia,  or  suffocation.     It  is  evident  there  can  be  several 
varieties  of  asphyxia,  as   in  apparent  drowning,  strangulation 
and  hanging,  inhalation  of  gases,  etc. 

The  first  and  essential  thing  to  do  is  to  give  fresh  air. 
Remove  the  person  to  the  open  air  and  place  him  on  his  back. 
Remove  tight  clothing  about  the  throat  and  waist,  dash  on  cold 
water,  give  a  few  drops  of  ammonia  in  hot  water  or  hot  ginger 
tea.  Friction  applied  to  the  limbs  should  be  kept  up.  If 
necessary,  use  artificial  respiration  by  the  Sylvester  method 
(sec.  380). 

The  chief  dangers  from  poisoning  by  noxious  gases  come 
from  the  fumes  of  burning  coal  in  the  furnace,  stove,  or  range  ; 
from  "  blowing  out "  gas,  turning  it  down,  and  having  it  blown 
out  by  a  draught ;  from  the  foul  air  often  found  in  old  wells ; 
from  the  fumes  of  charcoal  and  the  foul  air  of  mines. 

378.  Apparent  Drowning.     Remove  all  tight  clothing  from 
the  neck,  chest,  and  waist.      Sweep  the  forefinger,  covered  with 
a  handkerchief  or  towel,  round  the  mouth,  to  free  it  from  froth 
and  mucus.     Turn  the  body  on  the  face,  raising  it  a  little,  with 
the  hands  under  the  hips,  to  allow  any  water  to  run  out  from 
the  air  passages.     Take  only  a  moment  for  this. 


32  PRACTICAL    PHYSIOLOGY. 

Lay  the  person  flat  upon  the  back,  with  a  folded  coat,  or  pad 
of  any  kind,  to  keep  the  shoulders  raised  a  little.  Remove  all 
the  wet,  clinging  clothing  that  is  convenient.  If  in  a  room  or 
sheltered  place,  strip  the  body,  and  wrap  it  in  blankets,  over- 
coats, etc.  If  at  hand,  use  bottles  of  hot  water,  hot  flats,  or 
bags  of  hot  sand  round  the  limbs  and  feet.  Watch  the  tongue  : 
it  generally  tends  to  slip  back,  and  to  shut  off  the  air  from  the 
glottis.  Wrap  a  coarse  towel  round  the  tip  of  the  tongue,  and 
keep  it  well  pulled  forward. 

The  main  thing  to  do  is  to  keep  up  artificial  respiration  until 
the  natural  breathing  comes,  or  all  hope  is  lost.  This  is  the 
simplest  way  to  do  it  :  The  person  lies  on  the  back ;  let  some 
one  kneel  behind  the  head.  Grasp  both  arms  near  the  elbows, 
and  sweep  them  upward  above  the  head  until  they  nearly  touch. 
Make  a  firm  pull  for  a  moment.  This  tends  to  fill  the  lungs 
with  air  by  drawing  the  ribs  up,  and  making  the  chest  cavity 
larger.  Now  return  the  arms  to  the  sides  of  the  body  until 
they  press  hard  against  the  ribs.  This  tends  to  force  out  the 


FIG.  163.  —  The  Sylvester  Method.     (First  movement  —  inspiration.) 

air.      This   makes   artificially  a  complete  act   of   respiration. 
Repeat  this  act  about  fifteen  times  every  minute. 

All  this  may  be  kept  up  for  several  hours.  The  first  sign  of 
recovery  is  often  seen  in  the  slight  pinkish  tinge  of  the  lips 
or  finger-nails.  That  the  pulse  cannot  be  felt  at  the  wrist 
is  of  little  value  in  itself  as  a  sign  of  death.  Life  may  be 


ACCIDENTS    AND    EMERGENCIES.  383 

present  when  only  the  most  experienced  ear  can  detect  the 
faintest  heart-beat. 

When  a  person  can  breathe,  even  a  little,  he  can  swallow. 
Hold  smelling-salts  or  hartshorn  to  the  nose.  Put  one  tea- 
spoonful  of  the  aromatic  spirits  of  ammonia,  or  even  of  am- 
monia water,  into  a  half-glass  of  hot  water,  and  give  a  few 
teaspoonfuls  of  this  mixture  every  few  minutes.  Meanwhile 
do  not  fail  to  keep  up  artificial  warmth  in  the  most  vigorous 
manner. 

379.  Methods  of  Artificial  Respiration.  There  are  several  well- 
established  methods  of  artificial  respiration.  The  two  known  as  the 
Sylvester  and  the  Marshall  Hall  methods  are  generally  accepted  as 
efficient  and  practical. 


FIG.  164.—  The  Sylvester  Method.     (Second  movement  —  expiration.) 

380.  The  Sylvester  Method.  The  water  and  mucus  are  sup- 
posed to  have  been  removed  from  the  interior  of  the  body  by  the 
means  above  described  (sec.  378). 

The  patient  is  to  be  placed  on  his  back,  with  a  roll  made  of  a  coat 
or  a  shawl  under  the  shoulders  ;  the  tongue  should  then  be  drawn 
forward  and  retained  by  a  handkerchief  which  is  placed  across  the 
extended  organ  and  carried  under  the  chin,  then  crossed  and  tied  at 
the  back  of  the  neck.  An  elastic  band  or  small  rubber  tube  or  a 
suspender  may  be  used  for  the  same  purpose. 


384  PRACTICAL  PHYSIOLOGY. 

The  attendant  should  kneel  at  the  head  and  grasp  the  elbows  of 
the  patient  and  draw  them  upward  until  the  hands  are  carried  above 
the  head  and  kept  in  this  position  until  one,  two,  three,  can  be  slowly 
counted.  This  movement  elevates  the  ribs,  expands  the  chest,  and 
creates  a  vacuum  in  the  lungs  into  which  the  air  rushes,  or  in  other 
words,  the  movement  produces  inspiration.  The  elbows  are  then 
slowly  carried  downward,  placed  by  the  side,  and  pressed  inward 
against  the  chest,  thereby  diminishing  the  size  of  the  latter  and  pro- 
ducing expiration. 

These  movements  should  be  repeated  about  fifteen  times  each 
minute  for  at  least  two  hours,  provided  no  signs  of  animation  show 
themselves. 

381.  The  Marshall  Hall  Method.  The  patient  should  be  placed 
face  downwards,  the  head  resting  on  the  forearm  with  a  roll  or  pillow 
placed  under  the  chest ;  he  should  then  be  turned  on  his  side,  an 


FIG.  165.  —  The  Marshall  Hall  Method.     (First  position.) 

assistant  supporting  the  head  and  keeping  the  mouth  open  ;  after  an 
interval  of  two  or  three  seconds,  the  patient  should  again  be  placed 
face  downward  and  allowed  to  remain  in  this  position  the  same  length 
of  time.  This  operation  should  be  repeated  fifteen  or  sixteen  times 
each  minute,  and  continued  (unless  the  patient  recovers)  for  at  least 
two  hours. 

If,  after  using  one  of  the  above  methods,  evidence  of  recovery 
appears,  such  as  an  occasional  gasp  or  muscular  movement,  the  efforts 
to  produce  artificial  respiration  must  not  be  discontinued,  but  kept  up 
until  respiration  is  fully  established.  All  wet  clothing  should  then  be 
removed,  the  patient  rubbed  dry,  and  if  possible  placed  in  bed,  where 


ACCIDENTS    AND    EMERGENCIES.  385 

warmth  .and  warm  drinks  can  be  properly  administered.  A  small 
amount  of  nourishment,  in  the  form  of  hot  milk  or  beef  tea,  should 
be  given,  and  the  patient  kept  quiet  for  two  or  three  days. 


FIG.  166.—  The  Marshall  Hall  Method.     (Second  position.) 

382.  Sunstroke  or  Heatstroke.  This  serious  accident,  so 
far-reaching  oftentimes  in  its  result,  is  due  to  an  unnatural 
elevation  of  the  bodily  temperature  by  exposure  to  the  direct 
rays  of  the  sun,  or  from  the  extreme  heat  of  close  and  confined 
rooms,  as  in  the  cook-rooms  and  laundries  of  hotel  basements, 
from  overheated  workshops,  etc. 

There  is  sudden  loss  of  consciousness,  with  deep,  labored 
breathing,  an  intense  burning  heat  of  the  skin,  and  a  marked 
absence  of  sweat.  The  main  thing  is  to  lower  the  temperature. 
Strip  off  the  clothing  ;  apply  chopped  ice,  wrapped  in  flannel  to 
the  head.  Rub  ice  over  the  chest,  and  place  pieces  under  the 
armpits  and  at  the  sides.  If  there  is  no  ice,  use  sheets  or 
cloths  wet  with  cold  water.  The  body  may  be  stripped,  and 
sprinkled  with  ice-water  from  a  common  watering-pot. 

If  the  skin  is  cold,  moist,  or  clammy,  the  trouble  is  due  to 
heat  exhaustion.  Give  plenty  of  fresh  air,  but  apply  no  cold 
to  the  body.  Apply  heat,  and  give  hot  drinks,  like  hot  ginger 
tea.  Sunstroke  or  heatstroke  is  a  dangerous  affliction.  It  is 
often  followed  by  serious  and  permanent  results.  Persons  who 
have  once  suffered  in  this  way  should  carefully  avoid  any  risk 
in  the  future. 


CHAPTER   XIV. 
IN    SICKNESS    AND   IN    HEALTH. 

383.  Arrangement  of  the  Sick-room.  This  room,  if  pos- 
sible, should  be  on  the  quiet  and  sunny  side  of  the  house. 
Pure,  fresh  air,  sunshine,  and  freedom  from  noise  and  odor  are 
almost  indispensable.  A  fireplace  as  a  means  of  ventilation  is 
invaluable.  The  bed  should  be  so  placed  that  the  air  may  get 
to  it  on  all  sides  and  the  nurse  move  easily  around  it.  Screens 
should  be  placed,  if  necessary,  so  as  to  exclude  superfluous 
light  and  draughts. 

The  sick-room  should  be  kept  free  from  all  odors  which  affect 
the  sick  unpleasantly,  as  perfumery,  highly  scented  soaps,  and 
certain  flowers.  Remove  all  useless  ornaments  and  articles 
likely  to  collect  dust,  as  unnecessary  pieces  of  furniture  and 
heavy  draperies.  A  clean  floor,  with  a  few  rugs  to  deaden  the 
footsteps,  is  much  better  than  a  woolen  carpet.  Rocking-chairs 
should  be  banished  from  the  sick-room,  as  they  are  almost  sure 
to  disturb  the  sick. 

A  daily  supply  of  fresh  flowers  tends  to  brighten  the  room. 
Keep  the  medicines  close  at  hand,  but  all  poisonous  drugs 
should  be  kept  carefully  by  themselves  and  ordinarily  under 
lock  and  key.  A  small  table  should  be  placed  at  the  bedside, 
and  on  it  the  bell,  food  tray,  flowers  and  other  small  things 
which  promote  the  comfort  of  the  patient. 

The  nurse  should  not  sleep  with  the  patient.  Sofas  and 
couches  are  not  commonly  comfortable  enough  to  secure  needed 
rest.  A  cot  bed  is  at  once  convenient  and  inexpensive,  and  can 
be  readily  folded  and  put  out  of  sight  in  the  daytime.  It  can 
also  be  used  by  the  patient  occasionally,  especially  during  con- 
valescence. 


IN    SICKNESS    AND    IN    HEALTH.  387 

384.  Ventilation  of  the  Sick-room.     Proper  ventilation  is 
most  essential  to  the  sick-room,  but  little  provision  is  ordinarily 
made  for  so  important  a  matter.     It  is  seldom  that  one  of  the 
windows  cannot  be  let  down  an  inch  or  more  at  the  top,  a 
screen  being  arranged  to  avoid  any  draught  on  the  patient. 
Remove  all  odors  by  ventilation  and  not  by  spraying  perfumery, 
or  burning  pastilles,  which  merely  conceal  offensive  odors  with- 
out purifying  the  air.     During  cold  weather  and  in  certain 
diseases,  the  patient  may  be  covered  entirely  with  blankets  and 
the  windows  opened  wide  for  a  few  minutes. 

Avoid  ventilation  by  means  of  doors,  for  the  stale  air  of  the 
house,  kitchen  smells,  and  noises  made  by  the  occupants  of 
the  house,  are  apt  to  reach  the  sick-room.  The  entire  air 
of  the  room  should  be  changed  at  least  two  or  three  times  a 
day,  in  addition  to  the  introduction  of  a  constant  supply  of 
fresh  air  in  small  quantities. 

385.  Hints  for  the   Sick-room.      Always   strive  to   look 
cheerful  and  pleasant  before  the  patient.     Whatever  may  hap- 
pen, do  not  appear  to  be  annoyed,  discouraged,  or  despondent. 
Do  your  best  to  keep  up  the  courage  of  sick  persons  under  all 
circumstances.     In  all  things  keep  in  constant  mind  the  comfort 
and  ease  of  the  patient. 

Do  not  worry  the  sick  with  unnecessary  questions,  idle  talk, 
or  silly  gossip.  It  is  cruel  to  whisper  in  the  sick-room,  for 
patients  are  always  annoyed  by  it.  They  are  usually  suspi- 
cious that  something  is  wrong  and  generally  imagine  that  their 
condition  has  changed  for  the  worse. 

Symptoms  of  the  disease  should  never  be  discussed  before 
the  patient,  especially  if  he  is  thought  to  be  asleep.  He  may 
be  only  dozing,  and  any  such  talk  would  then  be  gross  cruelty. 
Loud  talking  must,  of  course,  be  avoided.  The  directions  of 
the  physician  must  be  rigidly  carried  out  in  regard  to  visitors 
in  the  sick-room.  This  is  always  a  matter  of  foremost  impor- 


388  PRACTICAL    PHYSIOLOGY. 

tance,  for  an  hour  or  even  a  night  of  needed  sleep  and  rest 
may  be  lost  from  the  untimely  call  of  some  thoughtless  visitor. 
A  competent  nurse,  who  has  good  sense  and  tact,  should  be 
able  to  relieve  the  family  of  any  embarrassment  under  such 
circumstances. 

Do  not  ever  allow  a  kerosene  light  with  the  flame  turned 
down  to  remain  in  the  sick-room.  Use  the  lamp  with  the  flame 
carefully  shaded,  or  in  an  adjoining  room,  or  better  still,  use  a 
sperm  candle  for  a  night  light. 

Keep,  so  far  as  possible,  the  various  bottles  of  medicine, 
spoons,  glasses,  and  so  on  in  an  adjoining  room,  rather  than 
to  make  a  formidable  array  of  them  on  a  bureau  or  table  near 
the  sick-bed.  A  few  simple  things,  as  an  orange,  a  tiny 
bouquet,  one  or  two  playthings,  or  even  a  pretty  book,  may 
well  take  their  place. 

The  ideal  bed  is  single,  made  of  iron  or  brass,  and  provided 
with  woven  wire  springs  and  a  hair  mattress.  Feather-beds  are 
always  objectionable  in  the  sick-room  for  many  and  obvious 
reasons.  The  proper  making  of  a  sick-bed,  with  the  forethought 
and  skill  demanded  in  certain  diseases,  is  of  great  importance 
and  an  art  learned  only  after  long  experience.  The  same 
principle  obtains  in  all  that  concerns  the  lifting  and  the  moving 
of  the  sick. 

Sick  people  take  great  comfort  in  the  use  of  fresh  linen  and 
fresh  pillows.  Two  sets  should  be  used,  letting  one  be  aired 
while  the  other  is  in  use.  In  making  changes  the  fresh  linen 
should  be  thoroughly  aired  and  warmed  and  everything  in 
readiness  before  the  patient  is  disturbed. 

386.  Rules  for  Sick-room.  Do  not  deceive  sick  people. 
Tell  what  is  proper  or  safe  to  be  told,  promptly  and  plainly. 
If  a  physician  is  employed,  carry  out  his  orders  to  the  very 
letter,  as  long  as  he  visits  you.  Make  on  a  slip  of  paper  a  note 
of  his  directions.  Make  a  brief  record  of  exactly  what  to  do. 


IN    SICKNESS    AND    IN    HEALTH.  389 

the  precise  time  of  giving  medicines,  etc.  This  should  always 
be  done  in  serious  cases,  and  by  night  watchers.  Then  there 
is  no  guesswork.  You  have  the  record  before  you  for  easy 
reference.  All  such  things  are  valuable  helps  to  the  doctor. 

Whatever  must  be  said  in  the  sick-room,  say  it  openly  and 
aloud.  How  often  a  sudden  turn  in  bed,  or  a  quick  glance  of 
inquiry,  shows  that  whispering  is  doing  harm !  If  the  patient 
is  in  his  right  mind,  answer  his  questions  plainly  and  squarely. 
It  may  not  be  best  to  tell  all  the  truth,  but  nothing  is  gained 
in  trying  to  avoid  a  straightforward  reply. 

Noises  that  are  liable  to  disturb  the  patient,  in  other  parts  of 
the  house  than  the  sick-room,  should  be  avoided.  Sounds  of  a 
startling  character,  especially  those  not  easily  explained,  as  the 
rattling  or  slamming  of  distant  blinds  and  doors,  are  always 
irritating  to  the  sick. 

Always  attract  the  attention  of  a  patient  before  addressing 
him,  otherwise  he  may  be  startled  and  a  nervous  spell  be 
induced.  The  same  hint  applies  equally  to  leaning  or  sitting 
upon  the  sick-bed,  or  running  against  furniture  in  moving 
about  the  sick-room. 

387.  Rest  of  Mind  and  Body.  The  great  importance  of 
rest  for  the  sick  is  not  so  generally  recognized  as  its  value 
warrants.  If  it  is  worry  and  not  work  that  breaks  down  the 
mental  and  physical  health  of  the  well,  how  much  more  impor- 
tant is  it  that  the  minds  and  bodies  of  the  sick  should  be  kept  at 
rest,  free  from  worry  and  excitement !  Hence  the  skilled  nurse 
does  her  best  to  aid  in  restoring  the  sick  to  a  condition  of  health 
by  securing  for  her  patient  complete  rest  both  of  mind  and  body. 
To  this  end,  she  skillfully  removes  all  minor  causes  of  alarm, 
irritation,  or  worry.  There  are  numberless  ways  in  which  this 
may  be  done  of  which  space  does  not  allow  even  mention.  De- 
tails apparently  trifling,  as  noiseless  shoes,  quietness,  wearing 
garments  that  do  not  rustle,  use  of  small  pillows  of  different  sizes, 


39°  PRACTICAL  PHYSIOLOGY. 

and  countless  other  small  things  that  make  up  the  refinement 
of  modern  nursing,  play  an  important  part  in  building  up  the 
impaired  tissues  of  the  sick. 

388.  Care  of  Infectious  and  Contagious  Diseases. .   There 
are  certain  diseases  which  are  known  to  be  infectious  and  can 
be  communicated  from  one  person  to  another,  either  by  direct 
contact,  through  the  medium  of  the  atmosphere,  or  otherwise. 

Of  the  more  prevalent  infectious  and  contagious  diseases 
are  scarlet  fever,  diphtheria,  erysipelas,  measles,  and  typhoid  fever. 

Considerations  of  health  demand  that  a  person  suffering  from 
any  one  of  these  diseases  should  be  thoroughly  isolated  from 
all  other  members  of  the  family.  All  that  has  been  stated  in 
regard  to  general  nursing  in  previous  sections  of  this  chapter, 
applies,  of  course,  to  nursing  infectious  and  contagious  diseases. 
In  addition  to  these  certain  special  directions  must  be  always 
kept  in  mind. 

Upon  the  nurse,  or  the  person  having  the  immediate  charge 
of  the  patient,  rests  the  responsibility  of  preventing  the  spread 
of  infectious  diseases.  The  importance  must  be  fully  under- 
stood of  carrying  out  in  every  detail  the  measures  calculated 
to  check  the  spread  or  compass  the  destruction  of  the  germs 
of  disease. 

389.  Hints  on  Nursing  Infectious  and  Contagious  Diseases. 

Strip  the  room  of  superfluous  rugs,  carpets,  furniture,  etc.  Iso- 
late two  rooms,  if  possible,  and  have  these,  if  convenient,  at  the 
top  of  the  house.  Tack  sheets,  wet  in  some  proper  disinfectant, 
to  the  outer  frame  of  the  sick-room  door.  Boil  these  sheets 
every  third  day.  In  case  of  diseases  to  which  young  folks  are 
very  susceptible,  send  the  children  away,  if  possible,  to  other 
houses  where  there  are  no  children. 

Most  scrupulous  care  should  be  taken  in  regard  to  cleanli- 
ness and  neatness  in  every  detail.  Old  pieces  of  linen,  cheese- 
cloth, paper  napkins,  should  be  used  wherever  convenient  or 


IN    SICKNESS    AND    IN    HEALTH.  39 1 

necessary  and  then  at  once  burnt.  All  soiled  clothing  that  can- 
not well  be  burnt  should  be  put  to  soak  at  once  in  disinfectants, 
and  afterward  boiled  apart  from  the  family  wash.  Dishes  and 
all  utensils  should  be  kept  scrupulously  clean  by  frequent 
boiling.  For  the  bed  and  person  old  and  worn  articles  of 
clothing  that  can  be  destroyed  should  be  worn  so  far  as 
possible. 

During  convalescence,  or  when  ready  to  leave  isolation,  the 
patient  should  be  thoroughly  bathed  in  water  properly  disin- 
fected, the  hair  and  nails  especially  being  carefully  treated. 

Many  details  of  the  after  treatment  depend  upon  the  special 
disease,  as  the  rubbing  of  the  body  with  carbolized  vaseline 
after  scarlet  fever,  the  care  of  the  eyes  after  measles,  and 
other  particulars  of  which  space  does  not  admit  mention  here. 


POISONS   AND   THEIR   ANTIDOTES. 

390.  Poisons.  A  poison  is  a  substance  which,  if  taken  into 
the  system  in  sufficient  amounts,  will  cause  serious  trouble  or 
death.  For  convenience  poisons  may  be  divided  into  two 
classes,  irritants  and  narcotics. 

The  effects  of  irritant  poisons  are  evident  immediately 
after  being  taken.  They  burn  and  corrode  the  skin  or  mem- 
brane or  other  parts  with  which  they  come  in  contact.  There 
are  burning  pains  in  the  mouth,  throat,  stomach,  and  abdomen, 
with  nausea  and  vomiting.  A  certain  amount  of  faintness  and 
shock  is  also  present. 

With  narcotic  poisoning,  the  symptoms  come  on  more  slowly. 
After  a  time  there  is  drowsiness,  which  gradually  increases  until 
there  is  a  profound  sleep  or  stupor,  from  which  the  patient  can 
be  aroused  only  with  great  difficulty.  There  are  some  sub- 
stances which  possess  both  the  irritant  and  narcotic  properties 
and  in  which  the  symptoms  are  of  a  mixed  character. 


392  PRACTICAL    PHYSIOLOGY. 

391.  Treatment  of  Poisoning.     An  antidote  is  a  substance 
which  will  either  combine  with  a  poison  to  render  it  harmless, 
or  which  will  have  a  directly  opposite  effect  upon  the  body, 
thus  neutralizing  the  effect  of  the  poison.     Hence  in  treatment 
of  poisoning  the  first  thing  to  do,  if  you  know  the  special  poison, 
is  to  give  its  antidote  at  once. 

If  the  poison  is  unknown,  and  there  is  any  delay  in  obtaining 
the  antidote,  the  first  thing  to  do  is  to  remove  the  poison  from 
the  stomach.  Therefore  cause  vomiting  as  quickly  as  possible. 
This  may  be  done  by  an  emetic  given  as  follows :  Stir  a  table- 
spoonful  of  mustard  or  of  common  salt  in  a  glass  of  warm 
water  and  make  the  patient  swallow  the  whole.  It  will  usually 
be  vomited  in  a  few  moments.  If  mustard  or  salt  is  not  at 
hand,  compel  the  patient  to  drink  lukewarm  water  very  freely 
until  vomiting  occurs. 

Vomiting  may  be  hastened,  by  thrusting  the  forefinger  down 
the  throat.  Two  teaspoonfuls  of  the  syrup  of  ipecac,  or  a 
heaping  teaspoonful  of  powdered  ipecac  taken  in  a  cup  of 
warm  water,  make  an  efficient  emetic,  especially  if  followed 
with  large  amounts  of  warm  water. 

It  is  to  be  remembered  that  in  some  poisons,  as  certain  acids 
and  alkalies,  no  emetic  should  be  given.  Again,  for  certain 
poisons  (except  in  case  of  arsenic)  causing  local  irritation,  but 
which  also  affect  the  system  at  large,  no  emetic  should  be  given. 

392.  Reference  Table  of  Common  Poisons ;   Prominent 
Symptoms ;  Antidotes  and  Treatment.    The  common  poisons 
with  their  leading  symptoms,  treatment,  and  antidotes,  may  be 
conveniently  arranged  for  easy  reference  in  the  form  of  a  table. 

It  is  to  be  remembered,  of  course,  that  a  complete  mastery 
of  the  table  of  poisons,  as  set  forth  on  the  two  following  pages, 
is  really  a  physician's  business.  At  the  same  time,  no  one  of 
fair  education  should  neglect  to  learn  a  few  of  the  essential 
things  to  do  in  accidental  or  intentional  poisoning. 


IN    SICKNESS    AND    IN    HEALTH. 


393 


A  TABLE  OF  THE  MORE  COMMON  POISONS, 

With  their  prominent  symptoms,  antidotes,  and  treatment. 


POISON. 

Strong  Acids  : 
Muriatic, 
Nitric, 

Sulphuric  (vitriol), 
Oxalic. 


Alkalies  : 

Caustic   potash    and 

soda, 

Ammonia, 
Lye, 

Pearlash, 
Saltpeter. 

Arsenic  : 
Paris  green, 
Rough  on  rats, 
White  arsenic, 
Fowler's  solution, 
Scheele's  green. 


Other     Metallic    Poi- 
sons : 

Blue  vitriol, 
Copperas, 
Green  vitriol, 
Sugar  of  lead, 
Corrosive  sublimate, 
Bedbug  poison. 


Phosphorus  from 
Matches,  rat  poisons, 
etc. 


PROMINENT  SYMPTOMS. 

Burning  sensation  in 
mouth,  throat,  and  stom- 
ach ;  blisters  about  mouth  ; 
vomiting ;  great  weakness. 


Burning  sensation  in  the 
parts;  severe  pain  in  stom- 
ach; vomiting;  difficulty 
in  swallowing;  cold  skin; 
weak  pulse. 


Intense  pains  in  stom- 
ach and  bowels ;  thirst ; 
vomiting,  perhaps  with 
blood ;  cold  and  clammy 
skin. 


Symptoms  in  general, 
same  as  in  arsenical  poi- 
soning. With  lead  and 
mercury  there  may  be  a 
metallic  taste  in  the  mouth. 


Pain  in  the  stomach ; 
vomiting ;  purging ;  gen- 
eral collapse. 


ANTIDOTES  AND  TREAT- 
MENT. 

No  emetic.  Saleratus ; 
chalk  ;  soap ;  plaster  from 
the  wall ;  lime ;  magnesia  ; 
baking  soda  (3  or  4  tea- 
spoonfuls  in  a  glass  of 
water). 

No  emetic.  Olive  oil 
freely  ;  lemon  juice  ;  vine- 
gar ;  melted  butter  and 
vaseline ;  thick  cream. 


Vomit  patient  repeat 
edly ;  give  hydrated  oxid 
of  iron  with  magnesia,  usu- 
ally kept  by  druggists  for 
emergencies ;  follow  with 
strong  solution  of  common 
salt  and  water. 


Emetic  with  lead  ;  none 
with  copper  and  iron ;  white 
of  eggs  in  abundance  with 
copper ;  with  iron  and  lead 
give  epsom  salts  freely ; 
afterwards,  oils,  flour,  and 
water. 

No  emetic  -with  mercury  ; 
raw  eggs;  milk,  or  flour 
and  water. 

Cause  vomiting.  Strong 
soapsuds ;  magnesia  in  wa- 
ter. Never  give  oils. 


394 


PRACTICAL    PHYSIOLOGY. 


POISON. 
Opium : 
Morphine, 
Laudanum, 
Paregoric, 
Dover's  powder, 
Soothing  syrups, 
Cholera     and    diar- 
rhoea  mixtures. 

Carbolic  Acid: 
Creasote. 


PROMINENT  SYMPTOMS. 

Sleepiness  ;  dullness  ; 
stupor  ;  "  pinhole  "  pupils  ; 
slow  breathing ;  profuse 
sweat. 


Severe  pain  in  abdomen ; 
odor  of  carbolic  acid,  mu- 
cous membrane  in  and 
around  mouth  white  and 
benumbed ;  cold,  clammy 
skin. 


ANTIDOTES  AND  TREAT- 
MENT. 

Cause  vomiting.  Keep 
patient  awake  by  any 
means,  especially  by  vig- 
orous walking ;  give  strong 
coffee  freely ;  dash  cold 
water  on  face  and  chest. 


No  emetic.   Milk,  or  flour 
and  water ;  white  of  eggs. 


Numbness    everywhere ; 
great  weakness ;  cold  sweat. 


Eyes  bright,  with  pupil 
enlarged ;  dry  mouth  and 
throat. 


Vomit    patient    freely. 
Stimulating   drinks. 


Vomit  patient  freely. 


Aconite : 
Wolfsbane, 
Monkshood. 

Belladonna : 

Deadly  nightshade, 
Atropia. 

Various  Vegetable  Poi- 
sons : 

Wild  parsley, 
Indian  tobacco, 
Toadstools, 
Tobacco  plant, 
Hemlock, 

Berries  of  the  moun- 
tain ash, 
Bitter  sweet,  etc. 


393.  Practical  Points  about  Poisons.  Poisons  should  never 
be  kept  in  the  same  place  with  medicines  or  other  prepara- 
tions used  in  the  household.  They  should  always  be  put 
in  some  secure  place  under  lock  and  key.  Never  use  inter- 
nally or  externally  any  part  of  the  contents  of  any  package  or 


Stupor,     nausea,     great  Cause  brisk  vomiting. 

weakness,  and  other  symp-       Stimulating  drinks. 


toms  according  to  the  poi- 


IN    SICKNESS    AND    IN    HEALTH.  395 

bottle  unless  its  exact  nature  is  known.  If  there  is  the  least 
doubt  about  the  substance,  do  not  assume  the  least  risk,  but 
destroy  it  at  once.  Many  times  the  unknown  contents  of  some 
bottle  or  package  has  been  carelessly  taken  and  found  to  be 
poison. 

Careless  and  stupid  people  often  take,  by  mistake,  with  seri- 
ous, and  often  fatal,  results,  poisonous  doses  of  carbolic  acid, 
bed-bug  poison,  horse-liniment,  oxalic  acid,  and  other  poisons. 
A  safe  rule  is  to  keep  all  bottles  and  boxes  containing  poisonous 
substances  securely  bottled  or  packed,  and  carefully  labeled 
with  the  word  POISON  plainly  written  in  large  letters  across 
the  label.  Fasten  the  cork  of  a  bottle  containing  poison  to  the 
bottle  itself  with  copper  or  iron  wire  twisted  into  a  knot  at  the 
top.  This  is  an  effective  means  of  preventing  any  mistakes, 
especially  in  the  night. 

This  subject  of  poisons  assumes  nowadays  great  importance, 
as  it  is  a  common  custom  to  keep  about  stables,  workshops, 
bathrooms,  and  living  rooms  generally  a  more  or  less  formid- 
able array  of  germicides,  disinfectants,  horse-liniments,  insect- 
poisons,  and  other  preparations  of  a  similar  character.  For 
the  most  part  they  contain  poisonous  ingredients. 

BACTERIA. 

394.  Nature  of  Bacteria.  The  word  bacteria  is  the  name 
applied  to  very  low  forms  of  plant  life  of  microscopic  size. 
Thus,  if  hay  be  soaked  in  water  for  some  time,  and  a  few 
drops  of  the  liquid  are  examined  under  a  high  power  of  the 
microscope,  the  water  is  found  to  be  swarming  with  various 
forms  of  living  vegetable  organisms,  or  bacteria.  These  micro- 
scopic plants  belong  to  the  great  fungus  division,  and  consist 
of  many  varieties,  which  may  be  roughly  divided  into  groups, 
according  as  they  are  spherical,  rod-like,  spiral,  or  otherwise  in 
shape. 


39^  PRACTICAL    PHYSIOLOGY. 

Each  plant  consists  of  a  mass  of  protoplasm  surrounded  by 
an  ill-defined  cell  wall.  The  bacteria  vary  considerably  in 
size.  Some  of  the  rod-shaped  varieties  are  from  ^5  to  ^  of 
an  inch  in  length,  and  average  about  ^5  of  an  inch  in  diame- 
ter. It  has  been  calculated  that  a  space  of  one  cubic  milli- 
meter would  contain 
2  so,  000,000  of  these 
minute  organisms, 
and  that  they  would 
not  weigh  more  than 
a  milligram. 

Bacteria  are  pro- 
pagated   in    a    very 

J          riG.  160.  —  Examples  of  Micro-Orgamsms  called 
simple  manner.   The  Bacteria.     (Drawn  from  photographs.) 

parent     Cell     divides     A>  spheroidal  bacteria  (called  cocci)  in  pairs ;   B,  same  kind 

into  tWO  '    these   tWO        of  bacteria  in  chains;  C,  bacteria  found  in  pus  (grouped  in 

masses  like  a  bunch  of  grapes).     [Bacteria  in  A,  B,  and  C 

mtO  tWO  Others,  and        magnified  about  1000  diameters].     D,  bacteria  found  in  pus 
SO  On.       The  rapidity        (tendency  to  grow  in  the  form  of  chains).      [Magnified 
.  .  about  500  diameters.] 

with  which  these  or- 
ganisms multiply  under  favorable  conditions,  makes  them,  in 
some  cases,  most  dangerous  enemies.  It  has  been  calculated 
that  if  all  of  the  organisms  survived,  one  bacterium  would 
lead  to  the  production  of  several  billions  of  others  in  twenty- 
four  hours. 

395.  The  Struggle  of  Bacteria  for  Existence.  Like  all 
kinds  of  living  things,  many  species  of  bacteria  are  destroyed 
if  exposed  to  boiling  water  or  steam,  but  seem  able  to  endure 
prolonged  cold,  far  below  the  freezing-point.  Thus  ice  from 
ponds  and  rivers  may  contain  numerous  germs  which  resume 
their  activity  when  the  ice  is  melted.  Typhoid  fever  germs 
have  been  known  to  take  an  active  and  vigorous  growth  after 
they  have  been  kept  for  weeks  exposed  in  ice  to  a  temperature 
below  zero. 


IN    SICKNESS    AND    IN    HEALTH.  397 

The  bacteria  of  consumption  (bacillus  tuberculosis)  may 
retain  their  vitality  for  months,  and  then  the  dried  expectora- 
tion of  the  invalids  may  become  a  source  of  danger  to  those 
who  inhale  air  laden  with  such  impurities  (sec.  220  and  Fig.  94). 

Like  other  living  organisms,  bacteria  need  warmth,  mois- 
ture, and  some  chemical  compound  which  answers  for  food,  in 
order  to  maintain  the  phenomena  of  life.  Some  species  grow 
only  in  contact  with  air,  others  need  no  more  oxygen  than  they 
can  obtain  in  the  fluid  or  semi-fluid  which  they  inhabit. 

396.  Importance  of  Bacteria  in  Nature.  We  might  well 
ask  why  the  myriads  of  bacteria  do  not  devastate  the  earth 
with  their  marvelous  rapidity  of  propagation.  So  indeed 
they  might,  were  it  not  for  the  winds,  rains,  melting  snow 
and  ice  which  scatter  them  far  and  wide,  and  destroy  them. 

Again,  as  in  countless  other  species  of  living  organisms, 
bacteria  are  subject  to  the  relentless  law  which  allows  only 
the  fittest  to  survive.  The  bacteria  of  higher  and  more 
complex  types  devour  those  of  a  lower  type.  Myriads  per- 
ish in  the  digestive  tract  of  man  and  other  animals.  The 
excreta  of  some  species  of  bacteria  act  as  poison  to  destroy 
other  species. 

It  is  true  from  the  strictest  scientific  point  of  view  that  all 
living  things  literally  return  to  the  dust  whence  they  came.  While 
living  they  borrow  a  few  elementary  substances  and  arrange 
them  in  new  combinations,  by  aid  of  the  energy  given  them  by 
the  sun,  and  after  a  time  die  and  leave  behind  all  they  had 
borrowed  both  of  energy  and  matter. 

Countless  myriads  of  bacteria  are  silently  at  work  changing 
dead  animal  and  vegetable  matter  into  useful  substances.  In 
brief,  bacteria  prepare  food  for  all  the  rest  of  the  world. 
Were  they  all  destroyed,  life  upon  the  earth  would  be  impos- 
sible, for  the  elements  necessary  to  maintain  it  would  be 
embalmed  in  the  bodies  of  the  dead. 


39$  PRACTICAL    PHYSIOLOGY. 

397.  Action  of  Bacteria.  In  certain  well-known  processes 
bacteria  have  the  power  of  bringing  about  decomposition  of 
various  kinds.  Thus  a  highly  organized  fungus,  like  the  yeast 
plant,  growing  in  the  presence  of  sugar,  has  the  power  of 
breaking  down  this  complex  body  into  simpler  ones,  viz., 
alcohol  and  carbon  dioxid. 

In  the  same  way,  various  forms  of  bacteria  have  the  power 
of  breaking  down  complex  bodies  in  their  immediate  neighbor- 
hood, the  products  depending  upon  the  substance,  the  kind  of 
bacteria,  and  the  conditions  under  which  they  act.  Thus  the 
bacteria  lactis  act 
upon  the  milk  sugar 
present  in  milk,  and  j 
convert  it  into  lactic 
acid,  thus  bringing  V  Vi 
about  the  souring  of 

FIG.  169. —  Examples  of  Pathogenic  Bacteria. 
m  (Drawn  from  photographs.) 

NOW,    While     mOSt     A,  spiral  form  of  bacteria  found  in  cholera.    (Magnified  about 

SDecieS     Of     bacteria         roo°  diameters.)      B,  rod-shaped  bacteria  (called  bacilli) 

from  a  culture  obtained  in  anthrax  or  malignant  fustule 

are     harmless,     SOme        Of  tne  face.    Diseased  hides  carry  this  micro-organism,  and 
are  the  Cause  Of  Sick-        *^us  may  occasi°n  disease  among  those  who  handle  hides 
and  wool.     (Magnified  about  1000  diameters.) 

ness  and  death  when 

they  gain  admittance  to  the  body  under  certain  conditions. 
These  disease-producing  bacteria  (known  as  pathogenic),  when 
established  in  the  blood  and  tissues  of  the  body,  bring  about 
important  chemical  changes,  depending  upon  the  species  of 
bacteria,  and  also  produce  a  particular  form  of  disease.  The 
production  of  certain  diseases  by  the  agency  of  bacteria  has 
now  been  proved  beyond  all  doubt.  In  yellow  fever,  ery- 
sipelas, diphtheria,  typhoid  fever,  consumption  and  other  dis- 
eases, the  connection  has  been  definitely  established. 

The  evil  results  these  germs  of  disease  produce  vary  greatly 
in  kind  and  severity.  Thus  the  bacteria  of  Asiatic  cholera  and 
diphtheria  may  destroy  life  in  a  few  hours,  while  those  of  con- 


IN    SICKNESS    AND    IN    HEALTH.  399 

sumption  may  take  years  to  produce  a  fatal  result.  Again,  the 
bacteria  may  attack  some  particular  organ,  or  group  of  organs, 
and  produce  mostly  local  symptoms.  Thus  in  a  boil  there  is 
painful  swelling  due  to  the  local  effect  of  the  bacteria,  with 
slight  general  disturbance. 

398.  The  Battle  against  Bacteria.     When  we  reflect  upon 
the  terrible  ravages  made  by  infectious  diseases,  and  all  their 
attendant  evils  for  these  many  years,  we  can  the  better  appre- 
ciate the  work  done  of  late  years  by  tireless  scientists  in  their 
efforts  to  modify  the  activity  of  disease-producing  bacteria.     It 
is  now  possible  to  cultivate  certain  pathogenic  bacteria,  and 
by  modifying  the  conditions  under  which  they  are  grown,  to 
destroy  their  violence. 

In  brief,  science  has  taught  us,  within  certain  limitations, 
how  to  change  the  virulent  germs  of  a  few  diseases  into 
harmless  microbes. 

399.  Alcoholic  Fermentation  and  Bacteria.     Men  of  the 

lowest,  as  well  as  of  the  highest,  type  of  civilization  have  always 
known  that  when  the  sugary  juice  of  any  fruit  is  left  to  itself 
for  a  time,  at  a  moderately  warm  temperature,  a  change  takes 
place  under  certain  conditions,  and  the  result  is  a  liquid  which, 
when  drank,  produces  a  pronounced  effect  upon  the  body.  In 
brief,  man  has  long  known  how  to  make  for  himself  alcoholic 
beverages,  by  means  of  which  he  may  become  intoxicated  with 
their  poisonous  ingredients. 

Whether  it  is  a  degraded  South  Sea  Islander  making  a  crude 
intoxicant  from  a  sugary  plant,  a  Japanese  preparing  his 
favorite  alcoholic  beverage  from  the  fermentation  of  rice  by 
means  of  a  fungus  plant  grown  for  the  purpose,  a  farmer  of 
this  country  making  cider  from  fermenting  apple  juice,  or  a 
French  expert  manufacturing  costly  champagne  by  a  compli- 
cated process,  the  outcome  and  the  intent  are  one  and  the 


4OO  PRACTICAL    PHYSIOLOGY. 

same.  The  essential  thing  is  to  produce  an  alcoholic  bev- 
erage which  will  have  a  marked  physiological  effect.  This 
effect  is  poisonous,  and  is  due  solely  to  the  alcoholic  ingre- 
dient, without  which  man  would  have  little  or  no  use  for  the 
otherwise  harmless  liquid. 

While  the  practical  process  of  making  some  form  of  alcoholic 
beverage  has  been  understood  for  these  many  centuries,  the 
real  reason  of  this  remarkable  change  in  a  wholesome  fruit 
juice  was  not  known  until  revealed  by  recent  progress  in 
chemistry,  and  by  the  use  of  the  microscope.  We  know  now 
that  the  change  is  due  to  fermentation,  brought  about  from  the 
influence,  and  by  the  action,  of  bacteria  (sec.  125). 

In  other  words,  fermentation  is  the  result  of  the  growth  of  a 
low  form  of  vegetable  life  known  as  an  organised  ferment.  This 
ferment,  whether  it  be  the  commonly  used  brewer's  yeast,  or 
any  other  species  of  alcoholic  ferment,  has  the  power  to  decom- 
pose or  break  down  a  large  part  of  the  sugar  present  in  the 
liquid  into  alcohol,  which  remains  as  a  poison,  and  carbon 
dioxid,  which  escapes  more  or  less  completely. 

Thus  man,  ever  prone  to  do  evil,  was  once  obliged,  in  his 
ignorance,  to  make  his  alcoholic  drinks  in  the  crudest  manner  ; 
but  now  he  has  forced  into  his  service  the  latest  discoveries  in 
science,  more  especially  in  bacteriology,  that  he  may  manu- 
facture more  scientifically  and  more  economically  alcoholic 
beverages  of  all  sorts  and  kinds,  and  distribute  them  broadcast 
all  over  God's  earth  for  the  physical  and  moral  ruin  of  the 
people. 

DISINFECTANTS. 

400.  Disinfectants,  Antiseptics,  and  Deodorants.  The  word 
disinfectant  is  synonymous  with  the  term  bacteridde  or  germi- 
cide. A  disinfectant  is  a  substance  which  destroys  infectious 
material.  An  antiseptic  is  an  agent  which  may  hinder  the 


IN    SICKNESS    AND    IN    HEALTH.  4OI 

growth,  but  does  not  destroy  the  vitality,  of  bacteria.  A  deo- 
dorant is  not  necessarily  a  disinfectant,  or  even  an  antiseptic, 
but  refers  to  a  substance  that  destroys  or  masks  offensive 
odors. 

401.  Air  and  Water  as  Disinfectants.     Nature   has   pro- 
vided for  our  protection  two  most  efficient  means  of  disinfec- 
tion,— pure  air  (sec.  218)  and  pure  water  (sec.  119).     The 
air  of   crowded   rooms   contains  large   quantities   of  bacteria, 
whereas   in  pure  air  there  are  comparatively  few,  especially 
after  rain,  which   carries   them   to  the   earth.     Living  micro- 
organisms have  never  been  detected  in  breezes  coming  from 
the  sea,  but  in  those  blowing  out  from  the  shore  large  numbers 
may  be  found. 

In  water  tainted  with  organic  matter  putrefactive  bacteria  will 
flourish,  whereas  pure  water  is  fatal  to  their  existence.  Sur- 
face water,  because  it  comes  from  that  part  of  the  soil  where 
bacteria  are  most  active,  and  where  there  is  most  organic  mat- 
ter, generally  contains  great  quantities  of  these  organisms.  In 
the  deeper  strata  of  the  soil  there  is  practically  no  decomposi- 
tion of  organic  matter  going  on,  hence,  water  taken  from  deep 
sources  is  comparatively  free  from  bacteria.  For  this  reason, 
deep  well  water  is  greatly  to  be  preferred  for  drinking  purposes 
to  that  from  surface  wells. 

402.  Disinfectants.     It  is  evident  that  air  and  water  are 
not  always  sufficient  to  secure  disinfection,  and  this  must  be 
accomplished  by  other  means.     The   destruction  of  infected 
material  by  fire  is,  of  course,  a  sure  but  costly  means  of  disin- 
fection.     Dry  heat,    steam,   and   boiling   water   are  valuable 
disinfectants  and  do  not  injure  most  fabrics.     These  agents 
are  generally  used  in  combination  with  various  chemical  dis- 
infectants. 

Certain   chemical    agents   that   are   capable    of    destroying 


4O2  PRACTICAL    PHYSIOLOGY. 

micro-organisms  and  their  spores  have  come,  of  late  years, 
into  general  use.  A  form  of  mercury,  called  corrosive  subli- 
mate, is  a  most  efficacious  and  powerful  germicide,  but  is 
exceedingly  poisonous  and  can  be  bought  only  under  restric- 
tions.1 Carbolic  acid,  chloride  of  lime,  permanganate  of  potash, 
and  various  other  preparations  made  from  zinc,  iron,  and 
petroleum,  are  the  chemical  disinfectants  most  commonly  and 
successfully  used  at  the  present  time.  There  are  also  numerous 
varieties  of  commercial  disinfectants  now  in  popular  use,  such 
as  Platt's  chlorides,  bromo-chloral,  sanitas,  etc.,  which  have 
proved  efficient  germicides. 

INSTRUCTIONS  FOR  THE  MANAGEMENT  OF  CONTAGIOUS 

DISEASES. 

The  following  instructions  for  the  management  .of  contagious 
diseases  were  prepared  for  the  National  Board  of  Health  by 
an  able  corps  of  scientists  and  experienced  physicians. 

403.  Instructions  for  Disinfection.     Disinfection  is  the  de- 
struction of  the  poisons  of  infectious  and  contagious  diseases. 

Deodorizers,  or  substances  which  destroy  smells,  are  not 
necessarily  disinfectants,  and  disinfectants  do  not  necessarily 
have  an  odor.  Disinfection  cannot  compensate  for  want  of 
cleanliness  nor  of  ventilation. 

404.  Disinfectants  to  be  Employed,    i.  Roll  sulphur  (brim- 
stone); for  fumigation. 

2.  Sulphate  of  iron  (copperas)  dissolved  in  water  in  the  pro- 
portion of  one  and  a  half  pounds  to  the  gallon  ;  for  soil, 
sewers,  etc. 

1  Corrosive  sublimate  is  probably  the  most  powerful  disinfectant  known.  A  solu- 
tion of  one  part  in  2000  will  destroy  microscopic  organisms.  Two  teaspoonfuls  of 
this  substance  will  make  a  solution  strong  enough  to  kill  all  disease  germs. 

NOTE.  A  most  useful  little  manual  to  consult  in  connection  with  this  chapter  is 
the  Hand-Book  of  Sanitary  Information,  written  by  Roger  S.  Tracy,  Sanitary 
Inspector  of  the  New  York  City  Health  Department.  Price,  50  cents. 


IN    SICKNESS    AND    IN    HEALTH.  403 

3.  Sulphate  of  zinc  and  common  salt,  dissolved  together  in 
water  in  the  proportion  of  four  ounces  sulphate  and  two  ounces 
salt  to  the  gallon  ;  for  clothing,  bed-linen,  etc. 

405  How  to  Use  Disinfectants.  i.  In  the  sick-room. 
The  most  available  agents  are  fresh  air  and  cleanliness.  The 
clothing,  towels,  bed-linen,  etc.,  should,  on  removal  from  the 
patient,  and  before  they  are  taken  from  the  room,  be  placed  in 
a  pail  or  tub  of  the  zinc  solution,  boiling-hot,  if  possible. 

All  discharges  should  either  be  received  in  vessels  contain- 
ing copperas  solution,  or,  when  this  is  impracticable,  should  be 
immediately  covered  with  copperas  solution.  All  vessels  used 
about  the  patient  should  be  cleansed  with  the  same  solution. 

Unnecessary  furniture,  especially  that  which  is  stuffed,  car- 
pets, and  hangings,  should,  when  possible,  be  removed  from 
the  room  at  the  outset ;  otherwise  they  should  remain  for  sub- 
sequent fumigation  and  treatment. 

2.  Fumigation.  Fumigation  with  sulphur  is  the  only  prac- 
ticable method  for  disinfecting  the  house.  For  this  purpose, 
the  rooms  to  be  disinfected  must  be  vacated.  Heavy  clothing, 
blankets,  bedding,  and  other  articles  which  cannot  be  treated 
with  zinc  solution,  should  be  opened  and  exposed  during  fumi- 
gation, as  directed  below.  Close  the  rooms  as  tightly  as 
possible,  place  the  sulphur  in  iron  pans  supported  upon  bricks 
placed  in  washtubs  containing  a  little  water,  set  it  on  fire  by  hot 
coals  or  with  the  aid  of  a  spoonful  of  alcohol,  and  allow  the 
room  to  remain  closed  for  twenty-four  hours.  For  a  room 
about  ten  feet  square,  at  least  two  pounds  of  sulphur  should 
be  used  ;  for  larger  rooms,  proportionally  increased  quantities.1 

1  The  burning  of  sulphur  produces  sulphurous  acid,  which  is  an  irrespirable  gas. 
The  person  who  lights  the  sulphur  must,  therefore,  immediately  leave  the  room,  and 
after  the  lapse  of  the  proper  time,  must  hold  his  breath  as  he  enters  the  room  to  open 
the  windows  and  let  out  the  gas.  After  fumigation,  plastered  walls  should  be  white- 
washed, the  woodwork  well  scrubbed  with  carbolic  soap,  and  painted  portions  re- 
painted. 


404  PRACTICAL    PHYSIOLOGY. 

3.  Premises.     Cellars,  yards,  stables,  gutters,  privies,  cess- 
pools, water-closets,  drains,  sewers,  etc.,  should  be  frequently 
and  liberally  treated  with  copperas    solution.     The    copperas 
solution    is   easily  prepared  by  hanging   a  basket    containing 
about  sixty  pounds  of  copperas  in  a  barrel  of  water.1 

4.  Body  and  bed  clothing,  etc.       It  is  best  to  burn  all  arti- 
cles which  have  been  in  contact  with  persons  sick  with  con- 
tagious  or   infectious  diseases.      Articles  too  valuable  to  be 
destroyed  should  be  treated  as  follows  : 

(a)  Cotton,  linen,  flannels,  blankets,  etc.,  should  be  treated 
with  the  boiling-hot  zinc  solution  ;  introduce  piece  by  piece, 
secure  thorough  wetting,  and  boil  for  at  least  half  an  hour. 

(b)  Heavy  woolen   clothing,  silks,  furs,  stuffed  bed-covers, 
beds,  and  other  articles  which  cannot  be  treated  with  the  zinc 
solution,  should  be  hung  in  the  room  during  fumigation,  their 
surfaces   thoroughly  exposed  and  pockets   turned  inside  out. 
Afterward  they  should  be  hung  in  the  open  air,  beaten,  and 
shaken.     Pillows,  beds,  stuffed  mattresses,  upholstered  furni- 
ture, etc.,  should  be  cut  open,  the  contents  spread  out  and 
thoroughly  fumigated.      Carpets    are   best  fumigated  on    the 
floor,  but  should  afterward  be  removed  to  the  open  air  and 
thoroughly  beaten. 

l  Put  copperas  in  a  pail  of  water,  in  such  quantity  that  some  may  constantly  re- 
main undissolved  at  the  bottom.  This  makes  a  saturated  solution.  To  every  privy 
or  water-closet,  allow  one  pint  of  the  solution  for  every  four  persons  when  cholera  is 
about.  To  keep  privies  from  being  offensive,  pour  one  pint  into  each  seat,  night  and 
morning. 

Books  for  Collateral  Study.  Among  the  many  works  which  may  be  consulted 
with  profit,  the  following  are  recommended  as  among  those  most  useful :  Parkes' 
Elements  of  Health  ;  Canfield's  Hygiene  of  the  Sick-Room  ;  Coplin  &  Bevan's  Prac- 
tical Hygiene ;  Lincoln's  School  Hygiene;  Edward  Smith's  Health;  McSherry's 
Health;  American  Health  Primers  (12  little  volumes,  edited  by  Dr.  Keen  of  Phila- 
delphia) ;  Reynold's  Primer  of  Health ;  Corfield's  Health ;  Appleton's  Health 
Primers;  Clara  S.  Weeks'  Nursing;  Church's  Food;  Yeo's  Food  in  Health  and 
Disease  ;  Hampton's  Nursing,  its  Principles  and  Practice  ;  Price's  Nurses  and 
Nursing;  Cullinworth's  Manual  of  Nursing;  Wise's  Text-Book  of  Nursing 
(2  vols.) ;  and  Humphrey's  Manual  of  Nursing. 


CHAPTER    XV. 
EXPERIMENTAL    WORK    IN    PHYSIOLOGY. 

406.  The  Limitations  of  Experimental  Work  in  Physiology  in 
Schools.     Unlike  other  branches  of  science  taught  in  the  schools 
from  the  experimental  point  of  view,  the  study  of  physiology  has  its 
limitations.     The  scope  and  range  of  such  experiments  is  necessarily 
extremely  limited  compared  with  what  may  be  done  with  the  costly 
and  elaborate  apparatus  of  the  medical  laboratory.     Again,  the  foun- 
dation of  physiology  rests  upon  systematic  and  painstaking  dissec- 
tion of  the  dead  human  body  and  the  lower  animals,  which  mode  of 
study  very  properly  is  not  permitted  in  ordinary  school  work.    Experi- 
ments upon  the  living  human  body  and  the  lower  animals,  now  so 
generally  depended  upon  in  our  medical  and  more  advanced  scientific 
schools,  for  obvious  reasons  can  be  performed  only  in  a  crude  and 
quite  superficial  manner  in  secondary  schools. 

Hence  in  the  study  of  physiology  in  schools  many  things  must  be 
taken  for  granted.  The  observation  and  experience  of  medical  men, 
and  the  experiments  of  the  physiologist  in  his  laboratory  must  be 
depended  upon  for  data  which  cannot  be  well  obtained  at  first  hand 
by  young  students. 

407.  Value  of  Experiments  in  Physiology  in  Secondary  Schools. 

While  circumstances  and  regard  for  certain  proprieties  of  social  life 
forbid  the  use  of  a  range  of  experiments,  in  anatomy  and  physiology, 
such  as  are  permitted  in  other  branches  of  science  in  secondary 
schools,  it  by  no  means  follows  that  we  are  shut  out  altogether  from 
this  most  important  and  interesting  part  of  the  study.  However 
simple  and  crude  the  apparatus,  the  skillful  and  enthusiastic  teacher 

NOTE.  For  additional  suggestions  and  practical  helps  on  the  subject  of  experi- 
mental work  in  physiology  the  reader  is  referred  to  Blaisdell's  Hoiv  to  Teach 
Physiology,  a  handbook  for  teachers.  A  copy  of  this  pamphlet  will  be  sent  postpaid 
to  any  address  by  the  publishers  of  this  book  on  receipt  of  ten  cents. 


4O6  PRACTICAL    PHYSIOLOGY. 

has  at  his  command  a  wide  series  of  materials  which  can  be  profit- 
ably utilized  for  experimental  instruction.  As  every  experienced 
teacher  knows,  pupils  gain  a  far  better  knowledge,  and  keep  up  a 
livelier  interest  in  any  branch  of  science,  if  they  see  with  their  own 
eyes  and  do  with  their  own  hands  that  which  serves  to  illuminate  and 
illustrate  the  subject-matter. 

The  experimental  method  of  instruction  rivets  the  attention  and 
arouses  and  keeps  alive  the  interest  of  the  young  student ;  in  fact,  it  is 
the  only  true  method  of  cultivating  a  scientific  habit  of  study.1  The 
subject-matter  as  set  forth  on  the  printed  pages  of  this  book  should 
be  mastered,  of  course,  but  at  the  same  time  the  topics  discussed 
should  be  illuminated  and  made  more  interesting  and  practical  by  a 
well-arranged  series  of  experiments,  a  goodly  show  of  specimens,  and 
a  certain  amount  of  microscopical  work. 

408.  The  Question  of  Apparatus.  The  author  well  understands 
from  personal  experience  the  many  practical  difficulties  in  the  way  of 
providing  a  suitable  amount  of  apparatus  for  class-room  use.  If  there 
are  ample  funds  for  this  purpose,  there  need  be  no  excuse  or  delay  in 
providing  all  that  is  necessary  from  dealers  in  apparatus  in  the  larger 
towns,  from  the  drug  store,  markets,  and  elsewhere.  In  schools 
where  both  the  funds  and  the  time  for  such  purposes  are  limited, 
the  zeal  and  ingenuity  of  teachers  and  students  are  often  put  to  a 
severe  test.  Fortunately  a  very  little  money  and  a  great  deal  of 
ingenuity  and  patience  will  do  apparent  wonders  towards  providing  a 
working  supply  of  apparatus. 

l  "  While  physiology  is  one  of  the  biological  sciences,  it  should  be  clearly  recog- 
nized that  it  is  not,  like  botany  or  zoology,  a  science  of  observation  and  descrip- 
tion; but  rather,  like  physics  or  chemistry,  a  science  of  experiment.  While  the 
amount  of  experimental  instruction  (not  involving  vivisection  or  experiment  other- 
wise unsuitable)  that  may  with  propriety  be  given  in  the  high  school  is  neither  small 
nor  unimportant,  the  limitations  to  such  experimental  teaching,  both  as  to  kind  and 
as  to  amount,  are  plainly  indicated. 

"  The  obvious  limitations  to  experimental  work  in  physiology  in  the  high  school, 
already  referred  to,  make  it  necessary  for  the  student  to  acquire  much  of  the  desired 
knowledge  from  the  text-book  only.  Nevertheless,  much  may  be  done  by  a  thought- 
ful and  ingenious  teacher  to  make  such  knowledge  real,  by  the  aid  of  suitable  practi- 
cal exercises  and  demonstrations."  —  Report  of  the  Committee  of  Ten  on  Secondary 
School  Studies. 


EXPERIMENTAL    WORK    IN    PHYSIOLOGY. 


407 


It  will  be  noticed  that  many  of  the  experiments  in  the  preceding 
chapters  of  this  book  can  be  performed  with  very  simple,  and  often 
a  crude  and  home-made  sort  of  apparatus.  This  plan  has  been  rigidly 
followed  by  the  author,  first,  because  he  fully  realizes  the  limitations 
and  restrictions  of  the  subject ;  and  secondly,  because  he  wishes  to 
emphasize  the  fact  that  expensive  and  complicated  apparatus  is  by 
no  means  necessary  to  illustrate  the  great  principles  of  anatomy  and 
physiology. 

409.  Use  of  the  Microscope.  To  do  thorough  and  satisfactory 
work  in  physiology  in  our  higher  schools  a  compound  microscope  is 
almost  indispensable.  Inasmuch  as  many 
of  our  best  secondary  schools  are  equipped 
with  one  or  more  microscopes  for  use  in 
other  studies,  notably  botany,  it  is  much 
less  difficult  than  it  was  a  few  years  ago  to 
obtain  this  important  help  for  the  classes 
in  physiology. 

For  elementary  class  work  a  moderate- 
priced,  but  well-made  and  strong,  instrument 
should  be  provided.  If  the  school  does  not 
own  a  microscope,  the  loan  of  an  instrument 
should  be  obtained  for  at  least  a  few  weeks 
from  some  person  in  the  neighborhood. 

The  appearance  of  the  various  structures 
and  tissues  of  the  human  body  as  revealed 
by  the  microscope  possesses  a  curious  fas- 
cination for  every  observer,  especially  for 
young  people.  No  one  ever  forgets  the 
first  look  at  a  drop  of  blood,  or  the  circulation  of  blood  in  a  frog's 
foot  as  shown  by  the  microscope. 

NOTE.  For  detailed  suggestions  in  regard  to  the  manipulation  and  use  of  the 
microscope  the  student  is  referred  to  any  of  the  standard  works  on  the  subject.  The 
catalogues  of  scientific-instrument  makers  of  our  larger  cities  generally  furnish  a  list 
of  the  requisite  materials  or  handbooks  which  describe  the  use  of  the  various  micro- 
scopes of  standard  make. 

The  author  is  indebted  to  Bergen's  Elements  of  Botany  for  the  following  informa- 
tion concerning  the  different  firms  which  deal  in  microscopes.  "Several  of  the 


FIG.  170.  —  A  Compound 
Microscope. 


4O8  PRACTICAL    PHYSIOLOGY. 

German  makers  furnish  excellent  instruments  for  use  in  such  a  course  as  that  here 
outlined.  The  author  is  most  familar  with  the  Leitz  microscopes,  which  are  furnished 
by  Wm.  Krafft,  411  West  5gth  St.,  New  York  city,  or  by  the  Franklin  Educational 
Co.,  15  and  17  Harcourt  St.,  Boston.  The  Leitz  Stand,  No.  IV.,  can  be  furnished 
duty  free  (for  schools  only),  with  objectives  i,  3,  and  5,  eye-pieces  I.  and  III.,  for 
$24.50.  If  several  instruments  are  being  provided,  it  would  be  well  to  have  part  of 
them  equipped  with  objectives  3  and  7,  and  eye-pieces  I.  and  III. 

"  The  American  manufacturers,  Bausch  &  Lomb  Optical  Company,  Rochester, 
N.  Y.,  and  No.  130  Fulton  St.,  New  York  city,  have  this  year  produced  a  micro- 
scope of  the  Continental  type  which  is  especially  designed  to  meet  the  requirements 
of  the  secondary  schools  for  an  instrument  with  rack  and  pinion  coarse  adjustment 
and  serviceable  fine  adjustment,  at  a  low  price.  They  furnish  this  new  stand, 
'  AAB/  to  schools  and  teachers  at  '  duty-free'  rates,  the  prices  being  for  the  stand 
with  two  eye-pieces  (any  desired  power),  §-inch  and  $-inch  objectives,  $25.60.  or  with 
2-inch,  §-inch,  and  j-inch  objectives,  and  two  eye-pieces,  $29.20.  Stand  '  A,'  the 
same  stand  as  the  '  AAB,'  without  joint  and  with  sliding  tube  coarse  adjustment 
(as  in  the  Leitz  Stand  IV.),  and  with  three  eye-pieces  and  §-inch  and  }-mch  objectives, 
is  furnished  for  $20.40.  Stand  '  A,'  with  two  eye-pieces,  §-inch  and  £-inch  objectives, 
$20.40." 

410.  The  Use  of  the  Skeleton  and  Manikin.     The  study  of  the 
bones  by  the  help  of   a  skeleton    is    almost  a  necessity.      To  this 
intent,  schools  of  a  higher  grade  should  be  provided  both  with   a 
skeleton  and  a  manikin.     If  the  former  is  not  owned  by  the  school, 
oftentimes  a  loan  of  one  can  be  secured  of  some  medical  man  in  the 
vicinity.     Separate  bones  will  also  prove  useful.     In   fact,  there  is 
no  other  way  to  study  properly  the  structure  and  use  of  the  bones 
and  joints  than  by  the  bones  themselves.     A  good  manikin  is  also 
equally  serviceable,  although  not  so  commonly  provided  for  schools 
on  account  of  its  cost. 

411.  The  Question  of  Vivisection  and  Dissection.     There  should 
be  no  question  at  all  concerning  vivisection.     In  no  shape  or  form 
should  it  be  allowed  in  any  grade  of  our  schools.     Nor  is  there  any 
need  of  much  dissection  in  the  grammar-school  grades.     A  few  sim- 
ple dissections  to   be  performed  with  fresh  beef-joints,  tendons   of 
turkey  legs,  and  so  on,  will  never  engender  cruel  or  brutal  feelings 
toward  living  things.     In   the  lower  grades  a  discreet  teacher  will 
rarely  advise  his  pupils  to  dissect  a  dead  cat,  dog,  frog,  or  any  other 
animal.      Instead  of   actual  dissection,  the  pupils  should  examine 
specimens  efr  certain  parts  previously  dissected  by  the  teacher,  —  as 


EXPERIMENTAL    WORK    IN    PHYSIOLOGY.  409 

the  muscles  and  tendons  of  a  sheep,  the  heart  of  an  ox,  the  eye  of  a 
cod-fish,  and  so  on.  Even  under  these  restrictions  the  teacher  should 
not  use  the  knife  or  scissors  before  the  class  to  open  up  any  part  of 
the  specimen.  In  brief,  avoid  everything  that  can  possibly  arouse 
any  cruel  or  brutal  feeling  on  the  part  of  young  students. 

In  the  higher  schools,  in  normal  and  other  training  schools,  differ- 
ent conditions  prevail.  Never  allow  vivisection  in  any  form  what- 
ever, either  in  school  or  at  home.  Under  the  most  exact  restrictions 
students  in  these  schools  may  be  taught  to  make  a  few  simple 
dissections. 

Most  teachers  will  find,  however,  even  in  schools  of  a  higher 
grade,  that  the  whole  subject  is  fraught  with  many  difficulties.  It 
will  not  require  much  oftentimes  to  provoke  in  a  community  a  deal 
of  unjust  criticism.  A  teacher's  good  sense  and  discretion  are  often 
put  to  a  severe  test. 


ADDITIONAL   EXPERIMENTS. 

To  the  somewhat  extended  list  of  experiments  as  described  in  the  pre- 
ceding chapters  a  few  more  are  herewith  presented  which  may  be  used  as 
opportunity  allows  to  supplement  those  already  given. 

Experiment  193.  To  examine  "white  fibrous  tissue.  Snip  off  a  very  minute 
portion  from  the  muscle  of  a  rabbit,  or  any  small  animal  recently  dead. 
Tease  the  specimen  with  needles,  mount  in  salt  solution  and  examine  under 
a  high  power.  Note  the  course  and  characters  of  the  fibers. 

Experiment  194.  To  examine  elastic  tissue.  Tease  out  a  small  piece  of 
ligament  from  a  rabbit's  leg  in  salt  solution  ;  mount  in  the  same,  and  exam- 
ine as  before.  Note  the  curled  elastic  fibers. 

Experiment  195.  To  examine  areolar  tissue.  Gerftly  tease  apart  some 
muscular  fibers,  noting  that  they^are  attached  to  each  other  by  connective 
tissue.  Remove  a  little  of  this  tissue  to  a  slide  and  examine  as  before. 
Examine  the  matrix  with  curled  elastic  fiber  mixed  with  straight  white 
fibers. 

Experiment  196.  To  examine  adipose  tissue.  Take  a  bit  of  fat  from  the 
mesentery  of  a  rabbit.  Tease  the  specimen  in  salt  solution  and  mount  in 
the  same.  Note  the  fat  cells  lying  in  a  vascular  meshwork. 


41 0  PRACTICAL    PHYSIOLOGY. 

Experiment  197.  To  examine  connective  tissues.  Take  a  very  small  por- 
tion from  one  of  the  tendons  of  a  rabbit,  or  any  animal  recently  dead ; 
place  upon  a  glass  slide  with  a  drop  of  salt  solution  •.  tease  it  apart  with 
needles,  cover  with  thin  glass  and  examine  with  microscope.  The  fine 
wavy  filaments  will  be  seen.  Allow  a  drop  of  dilute  acetic  acid  to  run  under 
the  cover  glass;  the  filaments  will  swell  and  become  transparent. 

Experiment  198.  Tease  out  a  small  piece  of  ligament  from  the  rabbit's 
leg  in  salt  solution ;  mount  in  the  same,  and  examine  under  a  high  power. 
Note  the  curled  elastic  fibers. 

Experiment  199.  A  crude  experiment  to  represent  the  way  in  -which  a 
person's  neck  is  broken.  Bring  the  ends  of  the  left  thumb  and  the  left 
second  finger  together  in  the  form  of  a  ring.  Place  a  piece  of  a  wooden 
toothpick  across  it  from  the  middle  of  the  finger  to  the  middle  of  the 
thumb.  Put  the  right  forefinger  of  the  other  hand  up  through  the  front 
part  to  represent  the  odontoid  process  of  the  axis,  and  place  some  absorb- 
ent cotton  through  the  other  part  to  represent  the  spinal  cord.  Push  back- 
wards with  the  forefinger  with  just  enough  force  to  break  the  toothpick 
and  drive  its  fragrnents  on  to  the  cotton. 

Experiment  200.  To  illustrate  how  the  pulse-wave  is  transmitted  along 
an  artery.  Use  the  same  apparatus  as  in  Experiment  106,  p.  201.  Take 
several  thin,  narrow  strips  of  pine  wood.  Make  little  flags  by  fastening  a 
small  piece  of  tissue  paper  on  one  end  of  a  wooden  toothpick.  Wedge 
the  other  end  of  the  toothpick  into  one  end  of  the  strips  of  pine  wood. 
Use  these  strips  like  levers  by  placing  them  across  the  long  rubber  tube  at 
different  points.  Let  each  lever  compress  the  tube  a  little  by  weighting 
one  end  of  it  with  a  blackboard  eraser  or  book  of  convenient  size. 

As  the  pulse-wave  passes  along  under  the  levers  they  will  be  successively 
raised,  causing  a  slight  movement  of  the  tissue-paper  flags. 

Experiment  201.  The  dissection  of  a  sheep 's  heart.  Get  a  sheep's 
heart  with  the  lungs -attached,  as  the  position  of  the  heart  will  be  better 
understood.  Let  the  lungs  be  laid  upon  a  dish  so  that  the  heart  is  upper- 
most, with  its  apex  turned  toward  the  observer. 

The  line  of  fat  which  extends  from  the  upper  and  left  side  of  the  heart 
downwards  and  across  towards  the  right  side,  indicates  the  division  be- 
tween the  right  and  left  ventricles. 

Examine  the  large  vessels,  and,  by  reference  to  the  text  and  illustrations, 
make  quite  certain  which  are  the  aorta,  the  pulmonary  artery,  the  superior 
and  inferior  vena  cavce,  and  the  pulmonary  veins. 


EXPERIMENTAL    WORK    IN    PHYSIOLOGY.  411 

Tie  variously  colored  yarns  to  the  vessels,  so  that  they  may  be  distin- 
guished when  separated  from  the  surrounding  parts. 

Having  separated  the  heart  from  the  lungs,  cut  out  a  portion  of  the  wall 
of  the  right  ventricle  towards  its  lower  part,  so  as  to  lay  the  cavity  open. 
Gradually  enlarge  the  opening  until  the  chorda;  tendinece  and  the  flaps  of 
the  tricuspid  valve  are  seen.  Continue  to  lay  open  the  ventricle  towards  the 
pulmonary  artery  until  the  semilunar  valves  come  into  view. 

The  pulmonary  artery  may  now  be  opened  from  above  so  as  to  display 
the  upper  surfaces  of  the  semilunar  valves.  Remove  part  of  the  wall  of 
the  right  auricle,  and  examine  the  right  auriculo-ventricular  opening. 

The  heart  may  now  be  turned  over,  and  the  left  ventricle  laid  open  in  a 
similar  manner.  Notice  that  the  mitral  valve  has  only  two  flaps.  The 
form  of  the  valves  is  better  seen  if  they  are  placed  under  water,  and 
allowed  to  float  out.  Observe  that  the  walls  of  the  left  ventricle  are  much 
thicker  than  those  of  the  right. 

Open  the  left  auricle,  and  notice  the  entrance  of  the  pulmonary  veins, 
and  the  passage  into  the  ventricle. 

The  ventricular  cavity  should  now  be  opened  up  as  far  as  the  aorta,  and 
the  semilunar  valves  examined.  Cut  open  the  aorta,  and  notice  the  form 
of  the  semilunar  valves. 

Experiment  202.  To  show  the  circulation  in  a  frog's  foot  (see  Fig.  78, 
p.  192).  In  order  to  see  the  blood  circulating  in  the  membrane  of  a 
frog's  foot  it  is  necessary  to  firmly  hold  the  frog.  For  this  purpose  obtain 
a  piece  of  soft  wood,  about  six  inches  long  and  three  wide,  and  half  an  inch 
thick.  At  about  two  inches  from  one  end  of  this,  cut  a  hole  three-quarters 
of  an  inch  in  diameter  and  cover  it  with  a  piece  of  glass,  which  should  be 
let  into  the  wood,  so  as  to  be  level  with  the  surface.  Then  tie  up  the  frog 
in  a  wet  cloth,  leaving  one  of  the  hind  legs  outside.  Next,  fasten  a  piece 
of  cotton  to  each  of  the  two  longest  toes,  but  not  too  tightly,  or  the  circu- 
fation  will  be  stopped  and  you  may  hurt  the  frog. 

Tie  the  frog  upon  the  board  in  such  a  way  that  the  foot  will  just  come 
over  the  glass  in  the  aperture.  Pull  carefully  the  pieces  of  cotton  tied  to 
the  toes,  so  as  to  spread  out  the  membrane  between  them  over  the  glass. 
Fasten  the  threads  by  drawing  them  into  notches  cut  in  the  sides  of  the 
board.  The  board  should  now  be  fixed  by  elastic  bands,  or  by  any  other 
convenient  means,  upon  the  stage  of  the  microscope,  so  as  to  bring  the 
membrane  of  the  foot  under  the  object  glass. 

The  flow  of  blood  thus  shown  is  indeed  a  wonderful  sight,  and  never  to 
be  forgotten.  The  membrane  should  be  occasionally  moistened  with  water. 

Care  should  be  taken  not  to  occasion  any  pain  to  the  frog. 


412 


PRACTICAL  PHYSIOLOGY. 


Experiment  203.  To  illustrate  the  mechanics  of  respiration 1  (see  Experi- 
ment 122,  p.  234).  "  In  a  large  lamp-chimney,  the  top  of  which  is  closed  by 
a  tightly  fitting  perforated  cork  (A),  is  arranged  a  pair  of  rubber  bags  (C) 
which  are  attached  to  a  Y  connecting  tube  (B),  to  be  had  of  any  dealer  in 
chemical  apparatus  or  which  can  be  made  by  a  teacher  having  a  bunsen 
burner  and  a  little  practice  in  the  manipulation  of  glass  (Fig.  171).  From 
the  center  of  the  cork  is  attached  a  rubber  band 
by  means  of  a  staple  driven  through  the  cork,  the 
other  end  of  which  (D)  is  attached  to  the  center 
of  a  disk  of  rubber  (E)  such  as  dentists  use.  This 
disk  is  held  to  the  edge  of  the  chimney  by  a  wide 
elastic  band  (F).  There  is  a  string  (G)  also  at- 
tached to  the  center  of  the  rubber  disk  by  means 
of  which  the  diaphragm  may  be  lowered. 

Such  is  a  description  of  the  essentials  of  the 
model.  The  difficulties  encountered  in  its  con- 
struction are  few  and  easily  overcome.  In  the  first 
place,  the  cork  must  be  air-tight,  and  it  is  best 
made  so  by  pouring  a  little  melted  paraffin  over  it, 
care  being  taken  not  to  close  the  tube.  The  rubber 
bags  were  taken  from  toy  balloon-whistles. 

In  the  construction  of  the  diaphragm,  it  is  to  be 
remembered  that  it  also  must  be  air-tight,  and  in 
order  to  resemble  the  human  diaphragm,  it  must 

have  a  conical  appearance  when  at  rest.  In  order  to  avoid  making  any 
holes  in  the  rubber,  the  two  attachments  (one  of  the  rubber  band,  and  the 
other  of  the  string)  were  made  in  this  wise :  the  rubber  was  stretched  over 
a  button  having  an  eye,  then  under  the  button  was  placed  a  smaller  ring 
from  an  old  umbrella ;  to  this  ring  was  attached  the  rubber  band,  and  to 
the  eye  of  the  button  was  fastened  the  operating  string.  When  not  in 
use  the  diaphragm  should  be  taken  off  to  relieve  the  strain  on  the  rubber 
band." 

Experiment  204.  To  illustrate  the  action  of  the  intercostal  muscles  (see 
sec.  210).  The  action  of  the  intercostal  muscles  is  not  at  first  easy  to 
understand ;  but  it  will  be  readily  comprehended  by  reference  to  a  model 
such  as  that  represented  in  Fig.  172.  This  maybe  easily  made  by  the  stu- 
dent himself  with  four  laths  of  wood,  fastened  together  at  the  corners, 

1  This  ingenious  and  excellent  experiment  is  taken  from  the  New  York  School 
Journal  for  May,  1897,  for  which  paper  it  was  prepared  by  Charles  D.  Nason,  of 
Philadelphia. 


FIG.  171. 


EXPERIMENTAL    WORK    IN    PHYSIOLOGY. 


413 


A,  B,  C,  D,  with  pins  or  small  screws,  so  as  to  be  movable.  At  the  points 
E,  F,  G,  H,  pins  are  placed,  to  which  elastic  bands  may  be  attached  (A). 
B  D  represents  the  vertebral  column ;  A  C,  the  sternum ;  and  A  B  and 
C  D,  the  ribs.  The  elastic  band  F  G  represents  the  external  intercostal 
muscles,  and  E  H,  the  internal  intercostals. 

If   now  the   elastic  band  E    H  be  removed,  the  remaining  band,  F  G, 
will  tend  to  bring  the  two  points  to  which  it  is  attached,  nearer  together, 


FIG. 172. 

and  the  result  will  be  that  the  bars  A  B  and  C  D  will  be  drawn  upwards 
(B),  that  is,  in  the  same  direction  as  the  ribs  in  the  act  of  inspiration. 
When  the  elastic  band  E  H  is  allowed  to  exert  its  force,  the  opposite 
effect  will  be  produced  (C) ;  in  this  case  representing  the  position  of  the 
ribs  in  an  act  of  expiration. 

Experiment  205.  Pin  a  round  piece  of  bright  red  paper  (large  as  a  din- 
ner-plate) to  a  white  wall,  with  a  single  pin.  Fasten  a  long  piece  of  thread 
to  it,  so  it  can  be  pulled  down  in  a  moment.  Gaze  steadily  at  the  red  paper. 
Have  it  removed  while  looking  at  it  intently,  and  a  greenish  spot  takes  its 
place. 

Experiment  206.  Lay  on  different  parts  of  the  skin  a  small,  square 
piece  of  paper  with  a  small  central  hole  in  it.  Let  the  person  close  his 
eyes,  while  another  person  gently  touches  the  uncovered  piece  of  skin  with 
cotton  wool,  or  brings  near  it  a  hot  body.  In  each  case  ask  the  observed 
person  to  distinguish  between  them.  He  will  always  succeed  on  the  volar 
side  of  the  hand,  but  occasionally  fail  on  the  dorsal  surface  of  the  hand, 
the  extensor  surface  of  the  arm,  and  very  frequently  on  the  skin  of  the  back. 

Experiment  207.  Wheatstone*  s  fluttering  hearts.  Make  a  drawing  of  a 
red  heart  on  a  bright  blue  ground.  In  a  dark  room  lighted  by  a  candle 
hold  the  picture  below  the  level  of  the  eyes  and  give  it  a  gentle  to-and-fro 
motion.  On  continuing  to  look  at  the  heart  it  will  appear  to  move  or  flutter 
over  the  blue  background. 


414  PRACTICAL  PHYSIOLOGY. 

Experiment  208.  At  a  distance  of  six  inches  from  the  eyes  hold  a  veil 
or  thin  gauze  in  front  of  some  printed  matter  placed  at  a  distance  of  about 
two  feet.  Close  one  eye,  and  with  the  other  we  soon  see  either  the  letters 
distinctly  or  the  fine  threads  of  the  veil,  but  we  cannot  see  both  equally 
distinct  at  the  same  time.  The  eye,  therefore,  can  form  a  distinct  image 
of  a  near  or  distant  object,  but  not  of  both  at  the  same  time  ;  hence  the 
necessity  for  accommodation. 

Experiment  209.  Place  a  person  in  front  of  a  bright  light  opposite  a 
window,  and  let  him  look  at  the  light ;  or  place  one's  self  opposite  a  well- 
illuminated  mirror.  Close  one  eye  with  the  hand  and  observe  the  diameter 
of  the  other  pupil.  Then  suddenly  remove  the  hand  from  the  closed  eye  : 
light  falls  upon  it ;  at  the  same  time  the  pupil  of  the  other  eye  contracts. 

Experiment  210.  To  illustrate  the  blind  spot.  Marriott's  experiment. 
On  a  white  card  make  a  cross  and  a  large  dot,  either  black  or  colored. 
Hold  the  card  vertically  about  ten  inches  from  the  right  eye,  the  left  being 
closed.  Look  steadily  at  the  cross  with  the  right  eye,  when  both  the  cross 
and  the  circle  will  be  seen.  Gradually  approach  the  card  towrard  the  eye, 
keeping  the  axis  of  vision  fixed  on  the  cross.  At  a  certain  distance  the 
circle  will  disappear,  i.e.,  when  its  image  falls  on  the  entrance  of  the  optic 
nerve.  On  bringing  the  card  nearer,  the  circle  reappears,  the  cross,  of 
course,  being  visible  all  the  time  (see  Experiment  180,  p.  355). 

Experiment  211.  To  map  out  the  field  of -vision.  A  crude  method  is  to 
place  the  person  with  his  back  to  a  window,  ask  him  to  close  one  eye, 
stand  in  front  of  him  about  two  feet  distant,  hold  up  the  forefingers  of  both 
hands  in  front  of  and  in  the  plane  of  your  own  face.  Ask  the  person  to 
look  steadily  at  your  nose,  and  as  he  does  so  observe  to  what  extent  the 
fingers  can  be  separated  horizontally,  vertically,  and  in  oblique  directions 
before  they  disappear  from  his  field  of  vision. 

Experiment  212.  To  illustrate  imperfect  judgment  of  distance.  Close 
one  eye  and  hold  the  left  forefinger  vertically  in  front  of  the  other  eye,  at 
arm's  length,  and  try  to  strike  it  with  the  right  forefinger. 

On  the  first  trial  one  will  probably  fall  short  of  the  mark,  and  fail  to 
touch  it.  Close  one  eye,  and  rapidly  try  to  dip  a  pen  into  an  inkstand,  or 
put  a  finger  into  the  mouth  of  a  bottle  placed  at  a  convenient  distance.  In 
both  cases  one  will  not  succeed  at  first. 

In  these  cases  one  loses  the  impressions  produced  by  the  convergence  of 
the  optic  axes,  which  are  important  factors  in  judging  of  distance. 

Experiment  213.  Hold  a  pencil  vertically  about  twelve  inches  from 
the  nose,  fix  it  with  both  eyes,  close  the  left  eye,  and  then  hold  the  right 


EXPERIMENTAL    WORK    IN    PHYSIOLOGY.  415 

index  finger  vertically,  so  as  to  cover  the  lower  part  of  the  pencil.  With  a 
sudden  move,  try  to  strike  the  pencil  with  the  finger.  In  every  case  one 
misses  the  pencil  and  sweeps  to  the  right  of  it. 

Experiment  214.  To  illustrate  imperfect  judgment  of  direction.  As  the 
retina  is  spherical,  a  line  beyond  a  certain  length  when  looked  at  always 
shows  an  appreciable  curvature. 

Hold  a  straight  edge  just  below  the  level  of  the  eyes.  Its  upper  margin 
shows  a  slight  concavity. 

SURFACE   ANATOMY   AND   LANDMARKS. 

In  all  of  our  leading  medical  colleges  the  students  are  carefully 
and  thoroughly  drilled  on  a  study  of  certain  persons  selected  as 
models.  The  object  is  to  master  by  observation  and  manipulation  the 
details  of  what  is  known  as  surface  anatomy  and  landmarks.  Now 
while  detailed  work  of  this  kind  is  not  necessary  in  secondary  schools, 
yet  a  limited  amount  of  study  along  these  lines  is  deeply  interesting 
and  profitable.  The  habit  of  looking  at  the  living  body  with  anatom- 
ical eyes  and  with  eyes  at  our  fingers'  ends,  during  the  course  in 
physiology,  cannot  be  too  highly  estimated. 

In  elementary  work  it  is  only  fair  to  state  that  many  points  of  sur- 
face anatomy  and  many  of  the  landmarks  cannot  always  be  defined 
or  located  with  precision.  A  great  deal  in  this  direction  can,  how- 
ever, be  done  in  higher  schools  with  ingenuity,  patience,  and  a  due 
regard  for  the  feelings  of  all  concerned.  Students  should  be  taught 
to  examine  their  own  bodies  for  this  purpose.  Two  friends  may  thus 
work  together,  each  serving  as  a  "  model "  to  the  other. 

To  the  following  syllabus  may  be  added  such  other  similar  exer- 
cises as  ingenuity  may  suggest  or  time  permit. 

SYLLABUS. 

I.   BONY  LANDMARKS. 

i.  The  occipital  protuberance  can  be  distinctly  felt  at  the  back 
of  the  head.  This  is  always  the  thickest  part  (often  three-quarters 
of  an  inch  or  more)  of  the  skull-cap,  and  is  more  prominent  in  some 
than  in  others.  The  thinnest  part  is  over  the  temples,  where  it  may 
be  almost  as  thin  as  parchment. 


41 6  PRACTICAL    PHYSIOLOGY. 

2.  The  working  of  the  condyle  of  the  lower  jaw  vertically  and 
from  side  to  side  can  be  distinctly  felt  and  seen  in  front  of  the  ear. 
When  the  mouth  is  opened  wide,  the  condyle  advances  out  of  the 
glenoid  cavity,  and  returns  to  its  socket  when  the  mouth  is  shut.  In 
front  of  the  ear,  lies  the  zygoma,  one  of  the  most  marked  and  impor- 
tant landmarks  to  the  touch,  and  in  lean  persons  to  the  eye. 

3.  The  sliding  movement  of   the  scapula  on  the  chest  can  be 
properly  understood  only  on  the  living  subject.     It   can  move  not 
only  upwards  and  downwards,  as  in  shrugging  the  shoulders,  back- 
wards and  forwards,  as  in  throwing  back  the  shoulders,  but  it  has  a 
rotary  movement  round  a  movable  center.     This  rotation  is  seen 
while  the  arm  is  being  raised  from  the  horizontal  to  the  vertical  posi- 
tion, and  is  effected  by  the  cooperation  of  the  trapezius  with  the 
serratus  magnus  muscles. 

4.  The  patella,  or  knee-pan,  the  two  condyles  of  the  tibia,  the 
tubercle  on  the  tibia  for  the  attachment  of  the  ligament  of  the  patella, 
and  the  head  of  the  fibula  are  the  chief  bony  landmarks  of  the  knee. 
The  head  of  the  fibula  lies  at  the  outer  and  back  part  of  the  tibia. 
In  extension  of  the  knee,  the  patella  is  nearly  all  above  the  condyles. 
The  inner  border  of  the  patella  is  thicker  and  more  prominent  than 
the  outer,  which  slopes  down  toward  its  condyle. 

5.  The  short,  front  edge  of  the  tibia,  called  the  "  shin,"  and  the 
broad,  flat,  subcutaneous  surface  of  the  bone  can  be  felt  all  the  way 
down.     The  inner  edge  can  be  felt,  but  not  so  plainly. 

6.  The  head  of  the  fibula  is  a  good  landmark  on  the  outer  side 
of  the  leg,  about  one  inch  below  the  top  of  the  tibia.     Note  that  it 
is  placed  well  back,  and  that  it  forms  no  part  of  the  knee  joint,  and 
takes  no  share  in  supporting  the  weight.     The  shaft  of  the  fibula 
arches  backwards  and  is  buried  deep  among  the  muscles,  except  at 
the  lower  fourth,  which  can  be  distinctly  felt. 

7.  The  malleoli  form  the  great  landmarks  of  the  ankle.     The 
outer  malleolus  descends  lower  than  the  inner.     The  inner  malleolus 
advances  more  to  the  front  and  does  not  descend  so  low  as  the  outer. 

8.  The  line  of  the  clavicle,  or  collar  bone,  and  the  projection  of 
the  joint  at  either  end  of  it  can  always  be  felt.     Its  direction  is  not 
perfectly  horizontal,  but  slightly  inclined  downwards.     We  can  dis- 
tinctly feel  the  spine  of  the  scapula  and  its  highest  point,  the  acromion. 


EXPERIMENTAL    WORK    IN    PHYSIOLOGY.  417 

9.  Projecting  beyond  the  acromion  (the  arm  hanging  by  the  side), 
we  can  feel,  through  the  fibers  of  the  deltoid,  the  upper  part  of  the 
humerus.      It  distinctly  moves   under  the  hand   when  the   arm  is 
rotated.     It  is  not  the  head  of  the  bone  which  is  felt,  but  its  promi- 
nences (the  tuberosities).    The  greater,  externally  ;  the  lesser  in  front. 

10.  The  tttberosities  of  the  humerits  form  the  convexity  of  the 
shoulder.     When  the  arm  is  raised,  the  convexity  disappears, — there 
is  a  slight  depression  in  its  place.     The  head  of  the  bone  can  be  felt 
by  pressing  the  fingers  high  up  in  the  axilla. 

11.  The  humerus  ends  at  the  elbow  in  two  bony  prominences 
(internal  and  external  condyles).     The  internal  is  more  prominent. 
We  can  always  feel  the  olecranon.     Between  this  bony  projection  of 
the  ulna  and  the  internal  condyle  is  a  deep  depression  along  which  runs 
the  ulna  nerve  (commonly  called  the  "  funny  "  or  "  crazy  "  bone). 

12.  Turn  the  hand  over  with  the  palm  upwards,  and  the  edge  of 
the   ulna  can  be  felt  from    the   olecranon  to  the   prominent   knob 
(styloid   process)   at  the  wrist.      Turn  the  forearm  over  with  the 
palm  down,  and  the  head  of  the  ulna  can  be  plainly  felt  and  seen 
projecting  at  the  back  of  the  wrist. 

13.  The  upper  half  of  the  radius  cannot  be  felt  because  it  is  so 
covered  by  muscles  ;  the  lower  half  is  more  accessible  to  the  touch. 

14.  The  three  rows  of   projections  called  the   "  knuckles "    are 
formed  by  the  proximal  bones  of  the  several  joints.     Thus  the  first 
row  is  formed  by  the  ends  of  the  metacarpals,  the  second  by  the 
ends  of  the  first  phalanges,  and  the  third  by  the  ends  of  the  second 
phalanges.     That  is,  in  all  cases  the  line  of  the  joints  is  a  little  in 
advance  of  the  knuckles  and  nearer  the  ends  of  the  fingers. 

II.     MUSCULAR  LANDMARKS. 

1.  The  position  of  the  sterno-mastoid muscle  as  an  important  and 
interesting  landmark  of  the  neck  has  already  been  described  (p.  70). 

2.  If  the  left  arm  be  raised  to  a  vertical  position  and  dropped  to 
a  horizontal,  somewhat  vigorously,  the  tapering  ends  of  the  pectoralis 
major  and  the  tendons  of  the  biceps  and  deltoid  may  be  felt  by 
pressing  the  parts  in  the  axilla  between  the  fingers  and  thumb  of  the 
right  hand. 


41 8  PRACTICAL    PHYSIOLOGY. 

3.  The  appearance  of  the  biceps  as  a  landmark  of  the  arm  has 
already  been  described  (p.  70).     The  action  of  its  antagonist,  the 
triceps,  may  be  studied  in  the  same  manner. 

4.  The  sartorius  is  one  of  the  fleshy  landmarks  of  the  thigh,  as 
the  biceps  is  of  the  arm,  and  the  sterno-cleido-mastoid  of  the  neck. 
Its  direction  and  borders  may  be  easily  traced  by  raising  the  leg,  — 
a  movement  which  puts  the  muscle  in  action. 

5.  If  the  model  be  directed  to  stand  on  tiptoe,  both  of  the  large 
muscles  of  the  calf,  the  gastrocnemius  and  soleus,  can  be  distin- 
guished. 

6.  Direct  the  model,  while  sitting  upright,  to  cross  one  leg  over 
the  other,  using  his  utmost  strength.     The  great  muscles  of  the  inner 
thigh  are  fully  contracted.     Note  the  force  required  to  pull  the  legs 
to  the  ordinary  position. 

7.  With  the  model  lying  in  a  horizontal  position  with  both  legs 
firmly  held  together,  note  the  force  required  to  pull  the  feet  apart 
while  the  great  muscles  of  the  thigh  are  fully  contracted. 

8.  In  forcible  and  resisted  flexion  of  the  wrist  two  tendons  come 
up  in  relief.     On  the  outer  side  of  one  we  feel  the  pulse  at  the 
wrist,  the  radial  artery  here  lying  close  to  the  radius. 

9.  On  the  outer  side  of  the  wrist  we  can  distinctly  see  and  feel, 
when  in  action,  the  three  extensor  tendons  of  the  thumbs.     Between 
two  of  them  is  a  deep  depression  at  the  base  of  the  thumb,  which  the 
French  call  the  "  anatomical  tobacco  box." 

10.  The  relative  position  of  the  several  extensor  tendons  on  the 
back  of  the  wrist  and  fingers  as  they  play  in  their  grooves  over  the 
back  of  the  radius  and  ulna  can  be  distinctly  traced  when  the  several 
muscles  are  put  in  action. 

11.  There  are  several  strong  tendons  to  be  seen  and  felt  about 
the  ankle.     Behind  is  the  tendo  Achillis.     It  forms  a  high  relief  with 
a  shallow  depression  on  each  side  of  it.     Behind  both  the  inner  and 
outer  ankle  several  tendons  can  be  felt.     Over  the  front  of  the  ankle, 
when  the  muscles  are  in  action,  we  can  see  and  feel  several  tendons. 
They  start  up  like  cords  when  the  action  is  resisted.     They  are  kept 
in  their  proper  relative  position  by  strong  pulleys  formed  by  the 
annular  ligament.     Most  of  these  tendons  can  be  best  seen  by  stand- 
a  model  on  one  foot,  i.e.  in  unstable  equilibrium. 


EXPERIMENTAL    WORK    IN    PHYSIOLOGY.  419 


III.     LANDMARKS  OF  THE  HEART. 

To  have  a  general  idea  of  the  form  and  position  of  the  heart,  map 
its  outline  with  colored  pencils  or  crayon  on  the  chest  wall  itself,  or 
on  some  piece  of  clean,  white  cloth,  tightly  pinned  over  the  clothing 
A  pattern  of  the  heart  may  be  cut  out  of  pasteboard,  painted  red,  or 
papered  with  red  paper,  and  pinned  in  position  outside  the  clothing. 
The  apex  of  the  heart  is  at  a  point  about  two  inches  below  the  left 
nipple  and  one  inch  to  its  sternal  side.  This  point  will  be  between 
the  fifth  and  sixth  ribs,  and  can  generally  be  determined  by  feeling 
the  apex  beat. 


IV.     LANDMARKS  OF  A  FEW  ARTERIES. 

The  pulsation  of  the  temporal  artery  can  be  felt  in  front  of  the 
ear,  between  the  zygoma  and  the  ear.  The  facial  artery  can  be  dis- 
tinctly felt  as  it  passes  over  the  upper  jaw  at  the  front  edge  of  the 
masseter  muscle.  The  pulse  of  a  sleeping  child  can  often  be  counted 
at  the  anterior  fontanelle  by  the  eye  alone. 

About  one  inch  above  the  clavicle,  near  the  outer  border  of  the 
sterno-mastoid,  we  can  feel  the  pulsation  of  the  great  subclavian 
artery.  At  the  back  of  the  knee  the  popliteal  artery  can  be  felt  beat- 
ing. The  dorsal  artery  of  the  foot  can  be  felt  beating  on  a  line  from 
the  middle  of  the  ankle  to  the  interval  between  the  first  and  second 
metatarsal  bones. 

When  the  arm  is  raised  to  a  right  angle  with  the  body,  the  axillary 
artery  can  be  plainly  felt  beating  in  the  axilla.  Extend  the  arm  with 
palm  upwards  and  the  brachial  artery  can  be  felt  close  to  the  inner 
side  of  the  biceps.  The  position  of  the  radial  artery  is  described  in 
Experiment  102. 


GLOSSARY. 


Abdomen  (Lat.  abdo,  abdere,  to  conceal).     The  largest  cavity  of  the  body, 

containing  the  liver,  stomach,  intestines,  and  other  organs. 
Abductor  (Lat.  abduco,  to  draw  from).    A  muscle  which  draws  a  limb  from 

the  middle  line  of  the  body,  or  a  ringer  or  toe  from  the  middle  line  of 

the  foot  or  hand. 
Absorbents  (Lat.  absorbere,  to  suck  up).     The  vessels  which  take  part  in 

the  process  of  absorption. 
Absorption.     The  process  of  sucking  up  nutritive  or  waste  matters  by  the 

blood-vessels  or  lymphatics. 
Accommodation  of  the  Eye.     The  alteration  in  the  shape  of  the  crystalline 

lens,  which    accommodates,  or  adjusts,  the  eye  for  near  or  remote 

vision. 
Acetabulum   (Lat.   acetabulum,   a   small   vinegar-cup).      The  cup-shaped 

cavity  of  the  innominate  bone  for  receiving  the  head  of  the  femur. 
Acid   (Lat.  acidus,  from  acere,  to  be  sour).      A  substance  usually  sour, 

sharp,  or  biting  to  the  taste. 
Acromion  (Gr.  &Kpov,  the  tip,  and  a>/w>s,  the  shoulder).     The  part  of  the 

scapula  forming  the  tip  of  the  shoulder. 
Adam's  Apple.     An  angular  projection  of  cartilage  in  the  front  of  the 

neck.     It  may  be  particularly  prominent  in  men. 
Adductor  (Lat.  adduce,  to  draw  to).     A  muscle  which  draws  towards  the 

middle  line  of  the  body,  or  of  the  hand  or  foot. 
Adenoid  (Gr.  dS-^v,  a  gland).     Tissue  resembling  gland  tissue. 
Afferent  (Lat.  ad,  to,  andfero,  to  convey).     Vessels  or  nerves  carrying  the 

contents  or  impulses  from  the  periphery  to  the  center. 
Albumen,  or  Albumin  (Lat.  albus,  white).     An  animal  substance  resem- 
bling the  white  of  an  egg. 
Albuminuria.     A   combination   of  the   words   "  albumin "   and  "  urine." 

Presence  of  albumen  in  the  urine. 

Aliment  (Lat.  alo,  to  nourish).     That  which  affords  nourishment ;  food. 
Alimentary  (Lat.  alimentum,  food).     Pertaining  to  aliment,  or  food. 


422  GLOSSARY. 

Alimentary  Canal   (Lat.   alimentum).     The   tube  in  which  the  food  is 

digested  or  prepared  for  reception  into  the  blood. 

Alkali  (Arabic  al  kali,  the  soda  plant).     A  name  given  to  certain  sub- 
stances, such  as  soda,  potash,  and  the  like,  which  have  the  power  of 

combining  with  acids. 
Alveolar  (Lat.  alveolus,  a  little  hollow).     Pertaining  to  the   alveoli,   the 

cavities  for  the  reception  of  the  teeth. 
Amoeba  (Gr.  d/xe//3w,  to  change).     A   single-celled,  protoplasmic  organism, 

which  is  constantly  changing  its  form  by  protrusions  and  withdrawals 

of  its  substance. 
Amoeboid.     Like  an  amceba. 
Ampulla  (Lat.  ampulla,  a  wine-flask).     The  dilated  part  of  the  semicircular 

canals  of  the  internal  ear. 
Anabolism  (Gr.  dva[3d\\<t),  to  throw  or  build  up).     The  process  by  means 

of  which  simpler  elements  are  built  up  into  more  complex. 
Anaesthetics  (Gr.  (Lv,  without,    and   alff0v}ffla,  feeling).     Those  medicinal 

agents  which  prevent  the  feeling  of  pain,  such  as  chloroform,  ether, 

laughing-gas,  etc. 
Anastomosis  (Gr.  dvd,  by,  and  <rT6/j,a,  a  mouth).     The  intercommunication 

of  vessels. 
Anatomy   (Gr.   dmrtyuw,   to  cut  up).     The  science  which  describes  the 

structure  of  living  things.     The  word  literally  means  dissection. 
Antiseptic  (Lat.  anti,  against,  and  sepsis,  poison).     Opposing  or  counter- 
acting putrefaction. 

Antrum  (Lat.  antrum,  a  cave).     The  cavity  in  the  upper  jaw. 
Aorta  (Gr.  do/ar^,  from  detpo,  to  raise  up).     The  great  artery  that  rises' up 

from  the  left  ventricle  of  the  heart. 
Aponeurosis  (Gr.  d-n-6,  from,  and  vevpov,  a  nerve).     A  fibrous  membranous 

expansion  of  a  tendon ;  the  nerves  and  tendons  were  formerly  thought 

to  be  identical  structures,  both  appearing  as  white  cords. 
Apoplexy  (Gr.  diroir^&a,  a  sudden  stroke).     The  escape  of  blood  from  a 

ruptured  blood-vessel  into  the  substance  of  the  brain. 
Apparatus.     A  number  of  organs  of  various  sizes  and  structures  working 

together  for  some  special  object. 
Appendages  (Lat.  ad  and  pendeo,  to  hang  from).     Something  connected 

with  a  part. 
Aqueous  Humor  (Lat.  aqua,  water).     The  watery  fluid  occupying  the  space 

between  the  cornea  and  crystalline  lens  of  the  eye. 
Arachnoid  Membrane  (Gr.  dpdxvrj,  a  spider,  and  et'Sws,  like).     The  thin 

covering  of  the  brain  and  spinal  cord,  between  the  dura  mater  and  the 

pia  mater. 


GLOSSARY.  423 

Arbor  Vitae.     Literally,  "  the  tree  of  life  "  ;  a  name  given  to  the  peculiar 

appearance  presented  by  a  section  of  the  cerebellum. 
Areolar  (Lat.  areola,  a  small  space,  dim.  of  area).     A  term  applied  to  a 

connective  tissue  containing  small  spaces. 
Artery  (Gr.  ayp,  air,  and  reptw,  to  contain).     A  vessel  by  which  blood  is 

carried  away  from  the  heart.     It  was  supposed  by  the  ancients  to  con- 

tain only  air,  hence  the  name. 
Articulation  (Lat.  articulo,  to  form  a  joint).     The  more  or  less  movable 

union  of  bones,  etc.  ;  a  joint. 
Arytenoid  Cartilages  (Gr.  dpi/ream,  a  ladle).     Two  small  cartilages  of  the 

larynx,  resembling  the  mouth  of  a  pitcher. 
Asphyxia  (Gr.  d,  without,  and  cr0/£is,  the  pulse).    Literally,  "  without  pulse." 

Condition  caused  by  non-oxygenation  of  the  blood. 
Assimilation  (Lat.  ad,  to,  and  similis,  like).     The  conversion  of  food  into 

living  tissue. 
Asthma  (Gr.  a<r8/j.a,  a  gasping).    Spasmodic  affection  of  the  bronchial  tubes 

in  which  free  respiration  is  interfered  with,  owing  to  their  diminished 

caliber. 
Astigmatism  (Gr.  d,  without,  and  ffriy/ju,  a  point).     Irregular  refraction  of 

the  eye,  producing  a  blurred  image. 
Atrophy  (Gr.  d,  without,  and  rpoQ-f),  nourishment).     Wasting  of  a  part 

from  lack  of  nutrition. 

Auditory  Nerve  (Lat.  audio,  to  hear).     The  special  nerve  of  hearing. 
Auricle  (Lat.  auricula,  a  little  ear).     A  cavity  of  the  heart. 
Azygos  (Gr.  d,  without,  and  £vy6s,  a  yoke).     Without  fellow  ;  not  paired. 


Bacteria  (paKTrfpiov,  a  staff).     A  microscopic,  vegetable  organism;  certain 

species  are  active  agents  in  fermentation,  while  others  appear  to  be  the 

cause  of  infectious  diseases. 

Bactericide  (Bacterium  and  Lat.  caedere,  to  kill).     Same  as  germicide. 
Bile.     The  gall,  or  peculiar  secretion  of  the  liver  ;  a  viscid,  yellowish  fluid, 

and  very  bitter  to  the  taste. 
Biology  (Gr.  filos,  life,  and  \6yos,  discourse).     The  science  which  treats  of 

living  bodies. 
Bladder  (Saxon  bleddra,  a  bladder,  a  goblet).     A  bag,  or  sac,  serving  as  a 

receptacle  of  some  secreted  fluid,  as  the  gall  bladder,  etc.     The  recep- 

tacle of  the  urine  in  man  and  other  animals. 
Bright's  Disease.     A  group  of  diseases  of  the  kidney,  first  described  by 

Dr.  Bright,  an  English  physician. 
Bronchi  (Gr.  /3p67xos,  windpipe).     The  first  two  divisions,  or  branches,  of 

the  trachea  ;  one  enters  each  lung. 


424  GLOSSARY. 

Bronchial  Tubes.  The  smaller  branches  of  the  trachea  within  the  sub- 
stance of  the  lungs  terminating  in  the  air  cells. 

Bronchitis.  Inflammation  of  the  larger  bronchial  tubes ;  a  "  cold  "  affect- 
ing the  air  passages. 

Bunion.  An  enlargement  and  inflammation  of  the  first  joint  of  the  great 
toe. 

Bursa.  A  pouch  ;  a  membranous  sac  interposed  between  parts  which  are 
subject  to  movement,  one  on  the  other,  to  allow  them  to  glide  smoothly. 

Callus  (Lat.  calleo,  to  be  thick-skinned).  Any  excessive  hardness  of  the 
skin  caused  by  friction  or  pressure. 

Canal  (Lat.  canalis,  a  canal).     A  tube  or  passage. 

Capillary  (Lat.  capillus,  hair).  The  smallest  blood-vessels,  so  called 
because  they  are  so  minute. 

Capsule  (Lat.  capsula,  a  little  chest).     A  membranous  bag  enclosing  a  part. 

Carbon  Dioxid,  often  called  carbonic  acid.  The  gas  which  is  present  in  the 
air  breathed  out  from  the  lungs  ;  a  waste  product  of  the  animal  king- 
dom and  a  food  of  the  vegetable  kingdom. 

Cardiac  (Gr.  Kapdla,  the  heart).  The  cardiac  orifice  of  the  stomach  is  the 
upper  one,  and  is  near  the  heart ;  hence  its  name. 

Carnivorous  (Lat.  caro,  flesh,  and  voro,  to  devour).     Subsisting  upon  flesh. 

Carron  Oil.  A  mixture  of  equal  parts  of  linseed  oil  and  lime-water,  so 
called  because  first  used  at  the  Carron  Iron  Works  in  Scotland. 

Cartilage.  A  tough  but  flexible  material  forming  a  part  of  the  joints,  air 
passages,  nostrils,  ear;  gristle,  etc. 

Caruncle  (Lat.  caro,  flesh).  The  small,  red,  conical-shaped  body  at  the 
inner  angle  of  the  eye,  consisting  of  a  cluster  of  follicles. 

Casein  '(Lat.  caseus,  cheese).  The  albuminoid  substance  of  milk;  it  forms 
the  basis  of  cheese. 

Catarrh.  An  inflammation  of  a  mucous  membrane,  usually  attended  with 
an  increased  secretion  of  mucus.  The  word  is  often  limited  to  nasal 
catarrh. 

Cauda  Equina  (Lat.,  horse's  tail).  The  collection  of  large  nerves  descend- 
ing from  the  lower  end  of  the  spinal  cord. 

Cell  (Lat.  cella,  a  storeroom).  The  name  of  the  tiny  miscroscopic  ele- 
ments, which,  with  slender  threads  or  fibers,  make  up  most  of  the  body; 
they  were  once  believed  to  be  little  hollow  chambers ;  hence  the  name. 

Cement.     The  substance  which  forms  the  outer  part  of  the  fang  of  a  tooth. 

Cerebellum  (dim.  for  cerebrum,  the  brain).  The  little  brain,  situated 
beneath  the  posterior  third  of  the  cerebrum. 

Cerebrum.     The  brain  proper,  occupying  the  upper  portion  of  the  skull. 


GLOSSARY.  425 

Ceruminous  (Lat.  cerumen,  ear  wax).  A  term  applied  to  the  glands  secret- 
ing cerumen,  or  ear  wax. 

Chloral.     A  powerful  drug  and  narcotic  poison  used  to  produce  sleep. 

Chloroform.  A  narcotic  poison  generally  used  by  inhalation  ;  of  exten- 
sive use  in  surgical  operations.  It  produces  anaesthesia. 

Chondrin  (Gr.  xoi/fy>6s,  cartilage).  A  kind  of  gelatine  obtained  by  boiling 
cartilage. 

Chordae  Tendineae.     Tendinous  cords. 

Choroid  (Gr.  -^opLov,  skin,  and  e?5os,  form).     The  middle  coat  of  the  eyeball. 

Chyle  (Gr.  %v\6s,  juice).  The  milk-like  fluid  formed  by  the  digestion  of 
fatty  articles  of  food  in  the  intestines. 

Chyme  (Gr.  xu/i6s,  juice).  The  pulpy  liquid  formed  by  digestion  in  the 
stomach. 

Cilia  (pi.  of  cilium,  an  eyelash).  Minute  hair-like  processes  found  upon 
the  cells  of  the  air  passages  and  other  parts. 

Ciliary  Muscle.    A  small  muscle  of  the  eye  which  assists  in  accommodation. 

Circumvallate  (Lat.  circum,  around,  and  vallum,  a  rampart).  Surrounded 
by  a  rampart,  as  are  certain  papillae  of  the  tongue. 

Coagulation  (Lat.  coagulo,  to  curdle).  Applied  to  the  process  by  which 
the  blood  clots  or  solidifies. 

Cochlea  (Lat.  cochlea,  a  snail  shell).     The  spiral  cavity  of  the  internal  ear. 

Columnar  Carneae.     Fleshy  projections  in  the  ventricles  of  the  heart. 

Commissure  (Lat.  con,  together,  and  mitto,  missum,  to  put).  A  joining  or 
uniting  together. 

Compress.     A  pad  or  bandage  applied  directly  to  an  injury  to  compress  it. 

Concha  (Gr.  KoyxVi  a  mussel  shell).  The  shell-shaped  portion  of  the 
external  ear. 

Congestion  (Lat.  con,  together,  and  gero,  to  bring).  Abnormal  gathering 
of  blood  in  any  part  of  the  body. 

Conjunctiva  (Lat.  con,  together,  and  jungo,  to  join).  A  thin  layer  of 
mucous  membrane  which  lines  the  eyelids  and  covers  the  front  of  the 
eyeball,  thus  joining  the  latter  to  the  lids. 

Connective  Tissue.  The  network  which  connects  the  minute  parts  of 
most  of  the  structures  of  the  body. 

Constipation  (Lat.  con,  together,  and  stipo,  to  crowd  close).     Costiveness. 

Consumption  (Lat.  consumo,  to  consume).  A  disease  of  the  lungs,  attended 
with  fever  and  cough,  and  causing  a  decay  of  the  bodily  powers.  The 
medical  name  is  phthisis. 

Contagion  (Lat.  con,  with,  and  tango  or  tago,  to  touch).  The  communica- 
tion of  disease  by  contact,  or  by  the  inhalation  of  the  effluvia  of  a  sick 
person. 


426  GLOSSARY. 

Contractility  (Lat.  con,  together,  and  traho,  to  draw).  The  property  of  a 
muscle  which  enables  it  to  contract,  or  draw  its  extremities  closer 
together. 

Convolutions  (Lat.  con,  together,  and  volvo,  to  roll).  The  tortuous  fold- 
ings of  the  external  surface  of  the  brain. 

Convulsion  (Lat.  convello,  to  pull  together).  A  more  or  less  violent  agita- 
tion of  the  limbs  or  body. 

Coordination.  The  manner  in  which  several  different  organs  of  the  body 
are  brought  into  such  relations  with  one  another  that  their  functions 
are  performed  in  harmony. 

Coracoid  (Gr.  /c6/ra£,  a  crow,  eiSos,  form).     Shaped  like  a  crow's  beak. 

Cornea  (Lat.  cornu,  a  horn).  The  transparent  horn-like  substance  which 
covers  a  part  of  the  front  of  the  eyeball. 

Coronary  (Lat.  corona,  a  crown).  A  term  applied  to  vessels  and  nerves 
which  encircle  parts,  as  the  coronary  arteries  of  the  heart. 

Coronoid  (Gr.  Kop&vr),  a  crow).  Like  a  crow's  beak;  thus  the  coronoid 
process  of  the  ulna. 

Cricoid  (Gr.  /cphcos,  a  ring,  and  e?5os,  form).  A  cartilage  of  the  larynx 
resembling  a  seal  ring  in  shape. 

Crystalline  Lens  (Lat.  crystallum,  a  crystal).  One  of  the  humors  of  the 
eye ;  a  double-convex  body  situated  in  the  front  part  of  the  eyeball. 

Cumulative.  A  term  applied  to  the  violent  action  from  drugs  which  super- 
venes after  the  taking  of  several  doses  with  little  or  no  effect. 

Cuticle  (Lat.  dim.  of  cutis,  the  skin).    Scarf  skin  ;  the  epidermis. 

Cutis  (Gr.  0-KUTos,  a  skin  or  hide).     The  true  skin,  also  called  the  dcrmis. 

Decussation  (Lat.  decusso,  decussatum,  to  cross).  The  crossing  or  running 
of  one  portion  athwart  another. 

Degeneration  (Lat.  degenerare,  to  grow  worse,  to  deteriorate).  A  change 
in  the  structure  of  any  organ  which  makes  it  less  fit  to  perform  its  duty. 

Deglutition  (Lat.  deglutire,  to  swallow).     The  process  of  swallowing. 

Deltoid.  Having  a  triangular  shape  ;  resembling  the  Greek  letter  A 
(delta). 

Dentine  (Lat.  dens,  dentis,  a  tooth).  The  hard  substance  which  forms 
the  greater  part  of  a  tooth  ;  ivory. 

Deodorizer.     An  agent  which  corrects  any  foul  or  unwholesome  odor. 

Dextrin.     A  soluble  substance  obtained  from  starch. 

Diabetes  Mellitus  (Gr.  Sid,  through,  pal™,  to  go,  and  /uAt,  honey).  Exces- 
sive flow  of  sugar-containing  urine. 

Diaphragm  (Gr.  diacfrpdcro-w,  to  divide  by  a  partition).  A  large,  thin  muscle 
which  separates  the  cavity  of  the  chest  from  the  abdomen. 


GLOSSARY.  427 

Diastole  (Gr.  Smo-reXXw,  to  dilate).     The  dilatation  of  the  heart. 

Dietetics.     That  part  of  medicine  which  relates  to  diet,  or  food. 

Diffusion  of  Gases.     The  power  of  gases  to  become  intimately  mingled. 

Diploe  (Gr.  5nrX6w,  to  double,  to  fold).  The  osseous  tissue  between  the 
tables  of  the  skull. 

Dipsomania  (Gr.  5tya,  thirst,  and  f^avla,  madness)..  An  insatiable  desire 
for  intoxicants. 

Disinfectants.  Agents  used  to  destroy  the  germs  or  particles  of  living 
matter  that  are  believed  to  be  the  causes  of  infection. 

Dislocation  (Lat.  dislocare,  to  put  out  of  place).  An  injury  to  a  joint  in 
which  the  bones  are  displaced  or  forced  out  of  their  sockets. 

Dissection  (Lat.  dis,  apart,  and  seco,  to  cut).  The  cutting  up  of  an  animal 
in  order  to  learn  its  structure. 

Distal  (Lat.  dis,  apart,  and  sto,  to  stand).     Away  from  the  center. 

Duct  (Lat.  duco,  to  lead).     A  narrow  tube. 

Duodenum  (Lat.  duodeni,  twelve).  The  first  division  of  the  small  intes- 
tines, about  twelve  fingers'  breadth  long. 

Dyspepsia  (Gr.  -5i/s,  ill,  and  irt-n-Teiv,  to  digest).  A  condition  of  the  ali- 
mentary canal  in  which  it  digests  imperfectly.  Indigestion. 

Dyspnoea  (Gr.  dfa,  difficult,  and  irvtw,  to  breathe).     Difficult  breathing. 

Efferent  (Lat.  effero,  to  carry  out).     Bearing  or  carrying  outwards,  as  from 

the  center  to  the  periphery. 
Effluvia  (Lat.  effluo,  to  flow  out).     Exhalations  or  vapors  coming  from  the 

body,  and  from  decaying  animal  or  vegetable  substances. 
Element.     One  of  the  simplest  parts  of  which  anything  consists. 
Elimination  (Lat.  <?,  out  of,  and  limen,  liminis,  a  threshold).     The  act  of 

expelling  waste  matters.     Signifies,  literally,  "  to  throw  out  of  doors." 
Emetic  (Gr.  ^w,  to  vomit).     A  medicine  which  causes  vomiting. 
Emulsion  (Lat.  emulgere,  to  milk).     Oil  in  a  finely  divided  state,  suspended 

in  water. 

Enamel  (Fr.  Entail}.     Dense  material  covering  the  crown  of  a  tooth. 
Endolymph  (Gr.  evdov,  within,  and  Lat.  lympha,  water).     The  fluid  in  the 

membranous  labyrinth  of  the  ear. 

Endosmosis  (Gr.  evdov,  within,  and  u)0e?w,  to  push).     The  current  from  with- 
out inwards  when  diffusion  of  fluids  takes  place  through  a  membrane. 
Epidemic  (Gr.  lirl,  upon,  and  S^uos,  the  people).'    An  extensively  prevalent 

disease. 
Epiglottis  (Gr.  tirl,  upon,  and  y\6rns,  the  entrance  to  the  windpipe).     A 

leaf-shaped  piece  of  cartilage  which  covers  the  top  of  the  larynx  during 

the  act  of  swallowing. 


428  GLOSSARY. 


Epilepsy  (Gr.  ^TrtXtj^is,  a  seizure).     A  nervous  disease  accompanied  by  fits 

in  which  consciousness  is  lost  ;  the  falling  sickness. 
Ether  (Gr.  aid^p,  the  pure,  upper  air).     A  narcotic  poison.     Used  as  an 

anaesthetic  in  surgical  operations. 
Eustachian  (from  an  Italian  anatomist  named  Eustachi).     The  tube  which 

leads  from  the  throat  to  the  middle  ear,  or  tympanum. 
Excretion  (Lat.  excerno,  to  separate).     The  separation  from  the  blood  of 

the  waste  matters  of  the  body  ;  also  the  materials  excreted. 
Exosmosis  (Gr.  e£w,  without,  and  wdtw,  to  push).     The  current  from  within 

outwards  when  diffusion  of  fluids  takes  place  through  a  membrane. 
Expiration  (Lat.  expiro,  to  breathe  out).     The  act  of  forcing  air  out  of  the 

lungs. 

Extension  (Lat.  ex,  out,  and  tendo,  to  stretch).     The  act  of  restoring  a  limb, 
•  etc.,  to  its  natural  position  after  it  has  been  flexed  or  bent  ;  the  opposite 

of  flexion, 

Fauces.     The  part  of  the  mouth  which  opens  into  the  pharynx. 
Fenestra  (Lat.).     Literally,  "a  window."     Fenestra  ovalis  and  fenestra 

rotunda,  the  oval  and  the  round  window  ;  two  apertures  in  the  bone 

between  the  tympanic  cavity  and  the  labyrinth  of  the  ear. 
Ferment.     That  which  causes  fermentation,  as  yeast. 
Fermentation  (  Lat.  ferme  ntum,  boiling).     The  process  of  undergoing  an 

effervescent  change,  as  by  the  action  of  yeast  ;  in  a  wider  sense,  the 

change  of  organized  substances  into  new  compounds  by  the  action  of  a 

ferment.     It  differs  in  kind  according  to  the  nature  of  the  ferment. 
Fiber  (Lak.jibra,  a  filament).    One  of  the  tiny  threads  of  which  many  parts  of 

the  body  are  composed. 
Fibrilla.     A   little  fiber;  one  of  the  longitudinal  threads  into  which   a 

striped  muscular  fiber  can  be  divided. 
Fibrin  (Lat.  fibra,  a  fiber).     An   albuminoid  substance  contained  in  the 

flesh  of  animals,  and  also  produced  by  the  coagulation  of  blood. 
Flexion  (Lat.  flecto,  to  bend).     The  act  of  bending  a  limb,  etc. 
Follicle  (Lat.  dim.  oifollis,  a  moneybag).     A  little  pouch  or  depression. 
Fomentation  (Ls&.foveo,  to  keep  warm).     The  application  of  any  warm, 

medicinal  substance  to  the  body,  by  which  the  vessels  are  relaxed. 
Foramen.     A  hole,  or  aperture. 
Frontal  Sinus.     A  blind  or  closed  cavity  in  the  bones  of  the  skull  just 

over  the  eyebrows. 
Fumigation  (Lat.  fumigo,  to  perfume  a  place).     The  use  of  certain  fumes, 

to  counteract  contagious  effluvia. 
Function  (La.t.  functio,  a  doing).     The  special  duty  of  any  organ. 


GLOSSARY.  429 

Ganglion    (Gr.   7077X101',   a  knot).     A  knot-like   swelling  in  a  nerve  ;  a 

smaller  nerve  center. 

Gastric  (Gr.  yacrnrip,  stomach).     Pertaining  to  the  stomach. 
Gelatine  (Lat.  gelo,  to  congeal).     An  animal  substance  which  dissolves  in 

hot  water  and  forms  a  jelly  on  cooling. 

Germ  (Lat.  germen,  a  sprout,  bud).     Disease  germ  ;  a  name  applied  to  cer- 
tain tiny  bacterial  organisms  which  have  been  demonstrated  to  be  the 

cause  of  disease. 
Germicide    (Germ,   and   Lat.  caedere,  to  kill).     Any  agent  which  has  a 

destructive  action  upon  living  germs,  especially  bacteria. 
Gland  (Lat.  glans,  an  acorn).     An  organ  consisting  of  follicles  and  ducts, 

with  numerous  blood-vessels  interwoven. 
Glottis  (Gr.  7\6TTd,  the  tongue).     The  narrow  opening  between  the  vocal 

cords. 

Glucose.     A  kind  of  sugar  found  in  fruits,  also  known  as  grape  sugar. 
Gluten.     The  glutinous  albuminoid  ingredient  of  cereals. 
Glycogen.     Literally,  "  producing  glucose."     Animal  starch  found  in  liver, 

which  may  be  changed  into  glucose. 
Gram.     Unit  of  metric  system,  1 5.43  grains  troy. 
Groin.     The  lower  part  of  the  abdomen,  just  above  each  thigh. 
Gustatory  (Lat.  gusto,  gustatum,  to  taste).     Belonging  to  the  sense  of  taste. 
Gymnastics  (Gr.  yvfj.vdfa,  to  exercise).     The  practice  of  athletic  exercises. 

Haemoglobin   (Gr.  afyia,  blood,  and  Lat.  globus,  a  globe  or  globule).     A 

complex  substance  which  forms  the  principal  coloring  constituent  of 

the  red  corpuscles  of  the  blood. 
Hemispheres   (Gr.  ^/u,/,  half,  and  0-0cupa,  a  sphere).     Half  a  sphere,  the 

lateral  halves  of  the  cerebrum,  or  brain  proper. 
Hemorrhage  (Gr.  af/«t,  blood,  and  p-fiyvvfju,  to  burst).    Bleeding,  or  the  loss 

of  blood. 

Hepatic  (Gr.  rfirap,  the  liver).     Pertaining  to  the  liver. 
Herbivorous  (Lat.  herba,  an  herb,  and  voro,  to  devour).  Applied  to  animals 

that  subsist  upon  vegetable  food. 
Heredity.     The  predisposition  or  tendency  derived  from  one's  ancestors 

to  definite  physiological  actions. 
Hiccough.     A  convulsive  motion  of  some  of  the  muscles  used  in  breathing, 

accompanied  by  a  shutting  of  the  glottis. 
Hilum,  sometimes  written  Hilus.     A  small  fissure,  notch,  or  depression. 

A  term  applied  to  the  concave  part  of  the  kidney. 
Homogeneous  (Gr.  6^65,  the  same,  and  ytvos,  kind).     Of  the  same  kind  or 

quality  throughout ;  uniform  in  nature,  —  the  reverse  of  heterogeneous. 


43°  GLOSSARY. 

Humor.     The  transparent  contents  of  the  eyeball. 

Hyaline  (Gr.  u'aXos,  glass).     Glass-like,  resembling  glass  in  transparency. 

Hydrogen.     An  elementary  gaseous  substance,  which,  in  combination  with 

oxygen,  produces  water. 
Hydrophobia  (Gr.  vdup,  water,  and  0oj3^o/icu,  to  fear).    A  disease  caused  by 

the  bite  of  a  rabid  dog  or  other  animal. 
Hygiene  (Gr.  vyleia,  health).     The  art  of  preserving  health  and  preventing 

disease. 
Hyoid  (Gr.  letter  v,  and  eT5os,  form,  resemblance).     The  bone  at  the  root 

of  the  tongue,  shaped  like  the  Greek  letter  v. 
Hypermetropia  (Gr.  irn-ty,  over,  beyond,  ^rpov,  measure,  and  u\f/,  the  eye). 

Far-sightedness. 
Hypertrophy  (Gr.  virtp,  over,  and  rpofi-/),  nourishment).    Excessive  growth ; 

thickening  or  enlargement  of  any  part  or  organ. 

Incisor  (Lat.  incido,  to  cut).     Applied  to  the  four  front  teeth  of  both  jaws, 

which  have  sharp,  cutting  edges. 

Incus.     An  anvil ;  the  name  of  one  of  the  bones  of  the  middle  ear. 
Indian  Hemp.     The  common  name  of  Cannabis  Indica,  an  intoxicating 

drug  known  as  hasheesh  and  by  other  names  in  Eastern  countries. 
Inferior  Vena  Cava.     The  chief  vein  of  the  lower  part  of  the  body. 
Inflammation  (Lat.  prefix  in  and  flammo,  to  flame).     A  redness  or  swelling 

of  any  part  of  the  body  with  heat  and  pain. 
Insalivation  (Lat.  in  and  saliva,  the  fluid  of  the  mouth).     The  mingling  of 

the  saliva  with  the  food  during  the  act  of  chewing. 
Inspiration  (Lat.  inspire,  spiratum,  to  breathe  in).     The  act  of  drawing  in 

the  breath. 
Intestine  (Lat.  intus,  within).     The  part  of  the  alimentary  canal  which  is 

continuous  with  the  lower  end  of  the  stomach;  also  called  the  bowels. 
Iris  (Lat.  iris,  the  rainbow).     The  thin,  muscular  ring  which  lies  between 

the  cornea  and  crystalline  lens,  giving  the  eye  its  special  color. 

Jaundice  (Fr.  jaunisse,  yellow).  A  disorder  in  which  the  skin  and  eyes 
assume  a  yellowish  tint. 

Katabolism  (Gr.  Karct/SdXXw,  to  throw  down).  The  process  by  means  of 
which  the  more  complex  elements  are  rendered  more  simple  and  less 
complex.  The  opposite  of  anabolism. 

Labyrinth.     The  internal  ear,  so  named  from  its  many  windings. 
Lacrymal  Apparatus  (Lat.  lacryma,  a  tear).     The  organs  for  forming  and 
carrying  away  the  tears. 


GLOSSARY.  43 1 

Lacteals  (Lat.  lac,  lactis,  milk).  The  absorbent  vessels  of  the  small 
intestines. 

Laryngoscope  (Gr.  \dpvy£,  larynx,  and  aKoirtu,  to  behold).  An  instrument 
consisting  of  a  mirror  held  in  the  throat,  and  a  reflector  to  throw  light 
on  it,  by  which  the  interior  of  the  larynx  is  brought  into  view. 

Larynx.     The  cartilaginous  tube  situated  at  the  top  of  the  windpipe. 

Lens.  Literally,  a  lentil ;  a  piece  of  transparent  glass  or  other  substance 
so  shaped  as  either  to  converge  or  disperse  the  rays  of  light. 

Ligament  (Lat.  ligoy  to  bind).  A  strong,  fibrous  material  binding  bones  or 
other  solid  parts  together. 

Ligature  (Lat.  ligo,  to  bind).  A  thread  of  some  material  used  in  tying  a 
cut  or  injured  artery. 

Lobe.     A  round,  projecting  part  of  an  organ,  as  of  the  liver,  lungs,  or  brain. 

Lymph  (Lat.  lympha,  pure  water).  The  watery  fluid  conveyed  by  the  lym- 
phatic vessels. 

Lymphatic  Vessels.     A  system  of  absorbent  vessels. 

Malleus.     Literally,  the  mallet  ;  one  of  the  small  bones  of  the  middle  ear. 

Marrow.     The  soft,  fatty  substance  contained  in  the  cavities  of  bones. 

Mastication  (Lat.  mastico,  to  chew).  The  act  of  cutting  and  grinding  the 
food  to  pieces  by  means  of  the  teeth. 

Meatus  (Lat.  meo,  meatum,  to  pass).     A.  passage  or  canal. 

Medulla  Oblongata.  The  "  oblong  marrow  " ;  that  portion  of  the  brain 
which  lies  upon  the  basilar  process  of  the  occipital  bone. 

Meibomian.  A  term  applied  to  the  small  glands  between  the  conjunctiva 
and  tarsal  cartilages,  discovered  by  Meibomius. 

Membrana  Tympani.  Literally,  the  membrane  of  the  drum  ;  a  delicate 
partition  separating  the  outer  from  the  middle  ear;  it  is  sometimes 
popularly  called  "the  drum  of  the  ear." 

Membrane.     A  thin  layer  of  tissue  serving  to  cover  some  part  of  the  body. 

Mesentery  (Gr.  /u&ros,  middle,  and  evrepov,  the  intestine).  A  duplicature  of 
the  peritoneum  covering  the  small  intestine,  which  occupies  the  middle 
or  center  of  the  abdominal  cavity. 

Metabolism  (Gr.  ^eTa/SoXiy,  change).  The  changes  taking  place  in  cells, 
whereby  they  become  more  complex  and  contain  more  force,  or  less  com- 
plex and  contain  less  force.  The  former  is  constructive  metabolism, 
or  anabolism  ;  the  latter,  destructive  metabolism,  or  katabolism . 

Microbe  (Gr.  /juKpbs,  little,  and  filos,  life).  A  microscopic  organism,  particu- 
larly applied  to  bacteria. 

Microscope  (Gr.  /MKp6s,  small,  and  (T/COTT^W,  to  look  at).  An  optical  instru- 
ment which  assists  in  the  examination  of  minute  objects. 


43 2  GLOSSARY. 

Molar   (Lat.  mola,  a  mill).     The  name  applied  to  the  three  back  teeth  at 

each  side  of  the  jaw ;  the  grinders,  or  mill-like  teeth. 
Molecule  (dim.  of  Lat.  moles,  a  mass).     The  smallest  quantity  into  which 

the  mass  of  any  substance  can  physically  be  divided.     A  molecule  may 

be  chemically  separated  into  two  or  more  atoms. 
Morphology  (Gr.  /u,6/>0?7,  form,  and  \6-yos,  discourse).     The  study  of  the  laws 

of  form  or  structure  in  living  beings. 

Motor  (Lat.  moveo,  motum,  to  move).     The  name  of  the  nerves  which  con- 
duct to  the  muscles  the  stimulus  which  causes  them  to  contract. 
Mucous  Membrane.     The  thin  layer  of  tissue  which  covers  those  internal 

cavities  or  passages  which  communicate  with  the  external  air. 
Mucus.     The  glairy  fluid  secreted  by  mucous  membranes. 
Myopia  (Gr.  /Atfw,  to  shut,  and  w^,  the  eye).     A  defect  of  vision  dependent 

upon  an  eyeball  that  is  too  long,  rendering  distant  objects  indistinct ; 

near  sight. 
Myosin  (Gr.  /xus,  muscle).     Chief  proteid  substance  of  muscle. 

Narcotic  (Gr.  rapccctw,  to  benumb).  A  medicine  which,  in  poisonous  doses, 
produces  stupor,  convulsions,  and  sometimes  death. 

Nerve  Cell.  A  minute  round  and  ashen-gray  cell  found  in  the  brain  and 
other  nervous  centers. 

Nerve  Fiber.     An  exceedingly  slender  thread  of  nervous  tissue. 

Nicotine.     The  poisonous  and  stupefying  oil  extracted  from  tobacco. 

Nostril  (Anglo-Saxon  nosu,  nose,  and  thyrl,  a  hole).  One  of  the  two  outer 
openings  of  the  nose. 

Nucleolus  (dim.  of  nucleus).     A  little  nucleus. 

Nucleus  (Lat.  nux,  a  nut).  A  central  part  of  any  body,  or  that  about  which 
matter  is  collected.  In  anatomy,  a  cell  within  a  cell. 

Nutrition  (Lat.  nutrio,  to  nourish).  The  processes  by  which  the  nourish- 
ment of  the  body  is  accomplished. 

Odontoid  (Gr.  65ous,  a  tooth,  eTSos,  shape).     The  name  of  the  bony  peg  of 

the  second  vertebra,  around  which  the  first  turns. 
(Esophagus.     Literally,  that  which  carries  food.     The  tube  leading  from 

the  throat  to  the  stomach  ;  the  gullet. 
Olecranon  (Gr.  u\£vq,  the  elbow,  and  Kpavlov,  the  top  of  the  head).     A 

curved  eminence  at  the  upper  and  back  part  of  the  ulna. 
Olfactory  (Lat.  olfacio,  to  smell).     Pertaining  to  the  sense  of  smell. 
Optic  (Gr.  <57rretfo;,  to  see).     Pertaining  to  the  sense  of  sight. 
Orbit  (Lat.  orbis,  a  circle).     The  bony  socket  or  cavity  in  which  the  eyeball 

is  situated. 


GLOSSARY.  433 

Organ  (Lat.  organum,  an  instrument  or  implement).  A  portion  of  the 
body  having  some  special  function  or  duty. 

Osmosis  (Gr.  oJ<r/>t6s,  impulsion).     Diffusion  of  liquids  through  membranes. 

Ossa  Innominata,  pi.  of  Os  Innominatum  (Lat.).  "  Unnamed  bones." 
The  irregular  bones  of  the  pelvis,  unnamed  on  account  of  their  non- 
resemblance  to  any  known  object. 

Otoconia  (Gr.  o5s,  an  ear,  and  Kovia,  dust).  Minute  crystals  of  lime  in  the 
vestibule  of  the  ear  ;  also  known  as  otoliths. 

Palate  (Lat.  palatum,  the  palate).     The  roof  of  the  mouth,  consisting  of  the 

hard  and  soft  palate. 
Palpitation   (Lat.  palpitatio,  a  frequent  or  throbbing  motion).     A  violent 

and  irregular  beating  of  the  heart. 

Papilla.     The  small  elevations  found  on  the  skin  and  mucous  membranes. 
Paralysis  (Gr.  TrapaXtfw,   to  loosen  ;    also,  to  disable).     Loss  of  function, 

especially  of  motion  or  feeling.     Palsy. 

Parasite.     A  plant  or  animal  that  grows  or  lives  on  another. 
Pelvis.     Literally,  a  basin.     The  bony  cavity  at  the  lower  part  of  the  trunk. 
Pepsin  (Gr.  TT^TTTW,  to  digest).     The  active  principle  of  the  gastric  juice. 
Pericardium  (Gr.  TTC/O/,  about,  and  Kapdia,  heart).     The  sac  enclosing  the 

heart. 

Periosteum  (Gr.  irepi,  around,  6<TTtov,  a  bone).     A  delicate  fibrous  mem- 
brane which  invests  the  bones. 
Peristaltic  Movements  (Gr.  irept,  round,  and  o-rAXa;,  to  send).     The  slow, 

wave-like  movements  of  the  stomach  and  intestines. 
Peritoneum  (Gr.  Tre/oire^w,  to  stretch  around).     The  investing  membrane 

of  the  stomach,  intestines,  and  other  abdominal  organs. 
Perspiration  (Lat.  perspiro,  to  breathe  through).     The  sweat. 
Petrous  (Gr.  ir^rpa,  a  rock).     The  name  of  the  hard  portion  of  the  temporal 

bone,  in  which  are  situated  the  drum  of  the  ear  and  labyrinth. 
Phalanges  (Gr.  (f>d\ayj-,  a  body  of  soldiers  closely  arranged  in  ranks  and 

files).     The  bones  of  the  fingers  and  toes. 
Pharynx  (Gr.  (pdpvyZ,   the  throat).     The  cavity  between  the  back  of  the 

mouth  and  the  gullet. 
Physiology  (Gr.  0&m,  nature,  and  \6yos,  a  discourse).     The  science  of  the 

functions  of  living,  organized  beings. 
Pia  Mater  (Lat.).     Literally,  the  tender  mother  ;  the  innermost  of  the  three 

coverings  of  the  brain.     It  is  thin  and  delicate  ;  hence  the  name. 
Pinna  (Lat.  a  feather  or  wing).     External  cartilaginous  flap  of  the  ear. 
Plasma  (Gr.  7rXd<ra-a>,  to  mould).      Anything  formed   or  moulded.     The 

liquid  part  of  the  blood. 


434  GLOSSARY. 

Pleura  (Gr.  -irXevpd,  the  side,  also  a  rib).  A  membrane  covering  the  lung, 
and  lining  the  chest. 

Pleurisy.     An  inflammation  affecting  the  pleura. 

Pneumogastric  (Gr.  irvetuwv,  the  lungs,  and  yourr-rip,  the  stomach).  The 
chief  nerve  of  respiration ;  also  called  the  vagus,  or  wandering  nerve. 

Pneumonia.     An  inflammation  affecting  the  air  cells  of  the  lungs. 

Poison  (Fr.  poison).  Any  substance,  which,  when  applied  externally,  or 
taken  into  the  stomach  or  the  blood,  works  such  a  change  in  the  animal 
economy  as  to  produce  disease  or  death. 

Pons  Varolii.  Bridge  of  Varolius.  The  white  fibers  which  form  a  bridge 
connecting  the  different  parts  of  the  brain,  first  described  by  Varolius. 

Popliteal  (Lat.  poples,  poplitis,  the  ham,  the  back  part  of  the  knee).  The 
space  behind  the  knee  joint  is  called  the  popliteal  space. 

Portal  Vein  (Lat.  porta,  a  gate).  The  venous  trunk  formed  by  the  veins 
coming  from  the  intestines.  It  carries  the  blood  to  the  liver. 

Presbyopia  (Gr.  irpfopvs,  old,  and  aty,  the  eye).  A  defect  of  the  accommo- 
dation of  the  eye,  caused  by  the  hardening  of  the  crystalline  lens ;  the 
"  far  sight  "  of  adults  and  aged  persons. 

Process  (Lat.  procedo,  processus,  to  proceed,  to  go  forth).  Any  projection 
from  a  surface ;  also,  a  method  of  performance  ;  a  procedure. 

Pronation  (Lat.  pronus,  inclined  forwards).  The  turning  of  the  hand  with 
the  palm  downwards. 

Pronator.     The  group  of  muscles  which  turn  the  hand  palm  downwards. 

Proteids  (Gr.  Trpwroj,  first,  and  efSos,  form).  A  general  term  for  the  albu- 
minoid constitutents  of  the  body. 

Protoplasm  (Gr.  Trpwros  first,  and  TrXtWco,  to  form).  A  first-formed  organ- 
ized substance ;  primitive  organic  cell  matter. 

Pterygoid  (Gr.  irrtpwv,  a  wing,  and  e?5os,  form,  resemblance).  Wing- 
like. 

Ptomaine  (Gr.  Trrw/xa,  a  dead  body).  One  of  a  class  of  animal  bases  or 
alkaloids  formed  in  the  putrefaction  of  various  kinds  of  albuminous 
matter. 

Ptyalin  (Gr.  <rla\ov,  saliva).  A  ferment  principle  in  saliva,  having  power  to 
convert  starch  into  sugar. 

Pulse  (Lat.  pello,  pulsum,  to  beat).  The  throbbing  of  an  artery  against  the 
finger,  occasioned  by  the  contraction  of  the  heart.  Commonly  felt  at 
the  wrist. 

Pupil  (Lat.  pupilla}.  The  central,  round  opening  in  the  iris,  through  which 
light  passes  into  the  interior  of  the  eye. 

Pylorus  (Gr.  irv\ovp6s,  a  gate-keeper).  The  lower  opening  of  the  stomach, 
at  the  beginning  of  the  small  intestine. 


GLOSSARY.  43  5 

Reflex  (Lat.  reflexus,  turned  back).  The  name  given  to  involuntary  move- 
ments produced  by  an  excitation  traveling  along  a  sensory  nerve  to  a 
center,  where  it  is  turned  back  or  reflected  along  motor  nerves. 

Renal  (Lat.  ren,  rents,  the  kidney).     Pertaining  to  the  kidneys. 

Respiration  (Lat.  respiro,  to  breathe  frequently).  The  function  of  breath- 
ing, comprising  two  acts,  —  inspiration,  or  breathing  in,  and  expiration, 
or  breathing  out. 

Retina  (Lat.  rete,  a  net).  The  innermost  of  the  three  tunics,  or  coats,  of 
the  eyeball,  being  an  expansion  of  the  optic  nerve; 

Rima  Glottidis  (Lat.  rima,  a  chink  or  cleft).     The  opening  of  the  glottis. 

Saccharine  (Lat.  saccharum,  sugar).  The  group  of  food  substances  which 
embraces  the  different  varieties  of  sugar,  starch,  and  gum. 

Saliva.  The  moisture,  or  fluids,  of  the  mouth,  secreted  by  the  salivary 
glands ;  the  spittle. 

Sarcolemma  (Gr.  <rdpt-,  flesh,  and  Xfy^a,  a  husk).  The  membrane  which 
surrounds  the  contractile  substance  of  a  striped  muscular  fiber. 

Sclerotic  (Gr.  tr/cX^s,  hard).     The  tough,  fibrous,  outer  coat  of  the  eyeball. 

Scurvy.  Scorbutus,  —  a  disease  of  the  general  system,  having  prominent 
skin  symptoms. 

Sebaceous  (Lat.  sebum,  fat).  Resembling  fat ;  the  name  of  the  oily  secre- 
tion by  which  the  skin  is  kept  flexible  and  soft. 

Secretion  (Lat.  secerno,  secretum,  to  separate).  The  process  of  separating 
from  the  blood  some  essential,  important  fluid;  which  fluid  is  also 
called  a  secretion. 

Semicircular  Canals.     Three  canals  in  the  internal  ear. 

Sensation.  The  perception  of  an  external  impression  by  the  nervous 
system. 

Serum.     The  clear,  watery  fluid  which  separates  from  the  clot  of  the  blood. 

Spasm  (Gr.  o-7rao-/i6s,  convulsion).  A  sudden,  violent,  and  involuntary  con- 
traction of  one  or  more  muscles. 

Special  Sense.  A  sense  by  which  we  receive  particular  sensations,  such 
as  those  of  sight,  hearing,  taste,  and  smell. 

Sputum,  pi.  Sputa  (Lat.  spuo,  sputum,  to  spit).  The  matter  which  is 
coughed  up  from  the  air  passages. 

Stapes.     Literally,  a  stirrup ;  one  of  the  small   bones  of  the  middle  ear. 

Stimulant  (Lat.  stimulo,  to  prick  or  goad  on).  An  agent  which  causes  an 
increase  of  vital  activity  in  the  body  or  in  any  of  its  parts. 

Striated  (Lat.  strio,  to  furnish  with  channels).     Marked  with  fine  lines. 

Styptics  (Gr.  0-TU7TTt/c6s,  astringent).  Substances  used  to  produce  a  contrac- 
tion or  shrinking  of  living  tissues. 


436  GLOSSARY. 

Subclavian  Vein  (Lat.  sub,  under,  and   clavis,  a  key).     The   great  vein 

bringing  back  the  blood  from  the  arm  and  side  of  the  head ;  so  called 

because  it  is  situated  underneath  the  clavicle,  or  collar  bone. 
Superior  Vena  Cava  (Lat.,  upper  hollow  vein).     The  great  vein  of  the 

upper  part  of  the  body. 
Suture  (Lat.  sutura,  a  seam).     The  union  of  certain  bones  of  the  skull  by 

the  interlocking  of  jagged  edges. 
Sympathetic  System  of  Nerves.     A  double   chain  of  nervous  ganglia, 

situated  chiefly  in  front  of,  and  on  each  side  of,  the  spinal  column. 
Symptom    (Gr.    <r6v,    with,    and    TT^TTTW,    to   fall).      A    sign   or   token    of 

disease. 
Synovial  (Gr.  o-tfj/,  with,  and  w6j>,  an  egg).     The  liquid  which  lubricates  the 

joints  ;  joint-oil.  It  resembles  the  white  of  a  raw  egg. 
System.  A  number  of  different  organs,  of  similar  structures,  distributed 

throughout  the  body  and  performing  similar  functions. 
Systemic.  Belonging  to  the  system,  or  body,  as  a  whole. 
Systole  (Gr.  o-uo-rAXw,  to  contract).  The  contraction  of  the  heart,  by  which 

the  blood  is  expelled  from  that  organ. 

Tactile  (Lat.  tactus,  touch).     Relating  to  the  sense  of  touch. 

Tartar.  A  hard  crust  which  forms  on  the  teeth,  and  is  composed  of  sali- 
vary mucus,  animal  matter,  and  a  compound  of  lime. 

Temporal  (Lat.  tempus,  time,  and  tempora,  the  temples).  Pertaining  to  the 
temples ;  so  called  because  the  hair  begins  to  turn  white  with  age  in 
that  portion  of  the  scalp. 

Tendon  (Lat.  tendo,  to  stretch).  The  white,  fibrous  cord,  or  band,  by 
which  a  muscle  is  attached  to  a  bone  ;  a  sinew. 

Tetanus  (Gr.  relva,  to  stretch).  A  disease  marked  by  persistent  contrac- 
tions of  all  or  some  of  the  voluntary  muscles  ;  those  of  the  jaw  are 
sometimes  solely  affected  ;  the  disorder  is  then  termed  lockjaw. 

Thorax  (Gr.  0ct>pa£,  a  breast-plate).  The  upper  cavity  of  the  trunk  of  the 
body,  containing  the  lungs,  heart,  etc.  ;  the  chest. 

Thyroid  (Gr.  %>£>*,  a  shield,  and  eI5os,  form).  The  largest  of  the  carti- 
lages of  the  larynx  :  its  projection  in  front  is  called  "  Adam's  Apple." 

Tissue.  Any  substance  or  texture  in  the  body  formed  of  various  elements, 
such  as  cells,  fibers,  blood-vessels,  etc.,  interwoven  with  each  other. 

Tobacco  (Indian  tabaco,  the  tube,  or  pipe,  in  which  the  Indians  smoked  the 
plant).  A  plant  used  for  smoking  and  chewing,  and  in  snuff. 

Trachea  (Gr.  Tpa-xjfe,  rough).     The  windpipe. 

Tragus  (Gr.  rpdyos,  a  goat).  The  eminence  in  front  of  the  opening  of  the 
ear ;  sometimes  hairy,  like  a  goat's  beard. 


GLOSSARY.  437 

Transfusion  (Lat.  trans/undo,  to  pour  from  one  vessel  to  another).  The 
operation  of  injecting  blood  taken  from  one  person  into  the  veins  of 
another. 

Trichina  Spiralis.  (A  twisted  hair).  A  minute  species  of  parasite,  or 
worm,  which  infests  the  flesh  of  the  hog :  may  be  introduced  into  the 
human  system  by  eating  pork  not  thoroughly  cooked. 

Trochanter  (Gr.  rpoxdw,  to  turn,  to  revolve).  Name  given  to  two  projec- 
tions on  the  upper  extremities  of  the  femur,  which  give  attachment  to 
the  rotator  muscles  of  the  thigh. 

Trypsin.  The  ferment  principle  in  pancreatic  juice,  which  converts  proteid 
material  into  peptones. 

Tubercle  (Lat.  tuber,  a  bunch).  A  pimple,  swelling,  or  tumor.  A  morbid 
product  occurring  in  certain  lung  diseases. 

Tuberosity  (Lat.  tuber,  tuberis,  a  swelling).     A  protuberance. 

Turbinated  (Lat.  turbinatus,  from  turbo,  turbinis,  a  top).  Formed  like  a 
top  ;  a  name  given  to  the  bones  in  the  outer  wall  of  the  nasal  fossae. 

Tympanum  (Gr.  Ttjuiravov,  a  drum).  The  cavity  of  the  middle  ear,  resem- 
bling a  drum  in  being  closed  by  two  membranes. 

Umbilicus  (Lat.,  the  navel.)     A  round  cicatrix  or  scar  in  the  median  line  of 

the  abdomen. 
Urea  (Lat.  urina,  urine).     Chief  solid  constitutent  of  urine.     Nitrogenous 

product  of  tissue  decomposition. 
Ureter  (Gr.  oup^w,  to  pass  urine).     The  tube  through  which  the  urine  is 

conveyed  from  the  kidneys  to  the  bladder. 
Uvula  (Lat.  uva,  a  grape).     The  small,  pendulous  body  attached  to  the 

back  part  of  the  palate. 

Vaccine  Virus  (Lat.  vacca,  a  cow,  and  virus,  poison).  The  material 
derived  from  heifers  for  the  purpose  of  vaccination,  —  the  great  pre- 
ventive of  smallpox. 

Valvulae  Conniventes.  A  name  given  to  transverse  folds  of  the  mucous 
membrane  in  the  small  intestine. 

Varicose  (Lat.  varix,  a  dilated  vein).     A  distended  or  enlarged  vein. 

Vascular  (Lat.  vasculum,  a  little  vessel).  Pertaining  to  or  possessing 
blood  or  lymph  vessels. 

Vaso-motor  (Lat.  vas,  a  vessel,  and  moveo,  motum,  to  move).  Causing 
motion  to  the  vessels.  Vaso-motor  nerves  cause  contraction  and  relaxa- 
tion of  the  blood-vessels. 

Venae  Cavae,  pi.  of  Vena  Cava.  "  Hollow  veins."  A  name  given  to  the 
two  great  veins  of  the  body  which  meet  at  the  right  auricle  of  the  heart. 


43  8  GLOSSARY. 

Venous  (Lat.  vena,  a  vein).     Pertaining  to,  or  contained  within,  a  vein. 
Ventilation.     The  introduction  of  fresh  air  into  a  room  or  building  in  such 

a  manner  as  to  keep  the  air  within  it  in  a  pure  condition. 
Ventral  (Lat.  venter,  ventris,  the  belly).     Belonging  to  the  abdominal  or 

belly  cavity. 

Ventricles  of  the  Heart.     The  two  largest  cavities  of  the  heart. 
Vermiform  (Lat.  vermis,  a  worm,  and  forma,  form).     Worm-shaped. 
Vertebral  Column  (Lat.  vertebra,  a  joint).     The  backbone  ;  also  called  the 

spinal  column  and  spine. 

Vestibule.     A  portion  of  the  internal  ear,  communicating  with  the  semi- 
circular canals  and  the  cochlea  ;  so  called  from  its  fancied  resemblance 

to  the  vestibule,  or  porch,  of  a  house. 
Villi  (Lat.  villus,  shaggy  hair).     Minute,  thread-like  projections  upon  the 

internal  surface  of  the  small  intestine,  giving  it  a  velvety  appearance. 
Virus  (Lat.,  poison).     Foul  matter  of  an  ulcer  ;  poison. 
Vital  Knot.     A  part  of  the  medulla  oblongata,  the  destruction  of  which 

causes  instant  death. 
Vitreous  (Lat.  vitrum,  glass).     Having  the  appearance  of  glass  ;  applied  to 

the  humor  occupying  the  largest  part  of  the  cavity  of  the  eyeball. 
Vivisection  (Lat.  vivus,  alive,  and  seco,  to  cut).     The  practice  of  operating 

upon  living  animals,  for  the  purpose  of  studying  some  physiological 

process. 
Vocal  Cords.     Two  elastic   bands  or  ridges  situated  in  the  larynx ;  the 

essential  parts  of  the  organ  of  voice. 

Zygoma  (Gr.  £vyt>v,  a  yoke).     The  arch  formed  by  the  malar  bone  and 
the  zygomatic  process  of  the  temporal  bone. 


INDEX. 


Absorption      .         .         .         .     144 

from  mouth  and  stomach      145 

by  the  intestines       .         .145 

Accident  and  emergencies       .     367 

Achilles,  Tendon  of         .         43, 65 

Air,  made  impure  by  breathing     221 

Foul,  effect  of,  on  health     222 

Alcohol,  Effect  of,  on  bones       53 

Effect  of,  on  muscles       .       72 

Effect    of,   on    muscular 

tissue  .  .  .  .  73 
Effect  of,  on  physical  cul- 
ture .  .  .  -95 
Nature  of  .  .  .112 
Effects  of,  on  human  sys- 
tem .  .  .  .114 
and  digestion  .  .  .  159 
Effect  of,  on  the  stomach  160 
and  the  gastric  juice  .  161 
Final  results  on  digestion  162 
Effects  of,  on  the  liver  .  163 
Fatty  degeneration  due  to  164 
Effect  of,  on  the  circula- 
tion ....  193 
Effect  of,  on  the  heart  .  195 
Effect  of,  on  the  blood- 
vessels .  .  .  .195 
Effect  of,  on  the  lungs  .  230 
Other  results  of,  on  lungs  231 
Effect  of,  on  disease  .  232 
Effect  of,  on  kidneys  .  261 


Alcohol,  as  cause  of  Blight's 

disease          .        .        .  262 

and  the  brain   .         .         .  294 

How,  injures  the  brain    .  295 

Why  brain  suffers  from  .  296 

the  enemy  of  brain  work  296 
Other  physical  results 

of          ....  297 

Diseases  produced  by      .  298 
Mental    and    moral   ruin 

by         ....  298 

Evil  results  of,  inherited  .  299 
Effect  of,  on  taste    .         -317 

Effect  of,  on  the  eye         .  340 
Effect  of,  on  throat  and 

voice     ....  365 

Alcoholic  beverages        .         .  1 1 1 
Alcoholic     fermentation    and 

Bacteria        .         .         .  399 

Anabolism  denned .         .         .  13 

Anatomy  defined    ...  4 

Antidotes  for  poisons     .         .  393 

Antiseptics      ....  400 

Apparatus,  Question  of  .         .  406 

Arm,  Upper    ....  36 

Arteries 180 

Astigmatism   ....  332 
Asphyxia         .         .         .         .381 
Atlas  and  axis          ...  34 
Atmosphere,   how    made    im- 
pure     ....  220 


440 


INDEX. 


Bacteria,  Nature  of         .         .     395 
Bacteria,    Struggle   for    exist- 
ence of          ...     396 
Importance  of,  in  Nature     397 
Action  of          ...     398 
Battle  against  .         .         .     399 
Baths  and  bathing  .         .         .     248 
Bathing,  Rules  and  precautions     2  50 
Bicycling         .         .         .  91 

Bile 138 

Biology  defined       ...         4 

Bladder 259 

Bleeding,  from  stomach  .         -374 

from  lungs        .         ,         .     374 

from  nose         .         .         -374 

How  to  stop    .        .     373,  374 

Blood,  Circulation  of      .      169,  184 

Physical  properties  of      .170 

corpuscles         .         .         -171 

Coagulation  of         .         .172 

Gene  ral  plan  of  circulati  on     1 74 

Blood-vessels,  Nervous  control 

of          ....     189 

connected  with  heart        .     179 

Effect  of  alcohol  on         .     195 

Injuries  to        .         .         -372 

Bodies,  living,  Characters  of         2 

Body,  General  plan  of    .         .       19 

Bone,  Chemical  composition  of       21 

Physical  properties  of       .       23 

Microscopic  structure  of  .       25 

Bones,  uses  of,  The         .         .       47 

Kinds  of  .         .         .         -47 

in  infancy  and  childhood       48 

positions  at  school  .         .       49 

in  after  life       ...       50 

Broken     .         .         .        51,  379 

broken,  Treatment  for,   52,  379 

Effect  of  alcohol  on          .       53 

Effect  of  tobacco  on         .       54 

Breathing,  Movements  of        .     211 


Breathing,  Mechanism  of 
Varieties  of 
Nervous  control  of  . 
change  in  the  air 
Air,  made  impure  by 

Brain,  as  a  whole    . 
Membranes  of 
as  a  reflex  center 


211 

212 
2I3 
217 
221 
268 

273 
284 


Effects  of  alcohol  on     294-297 
Brain  center,  Functions  of,  in 
perception    of    impres- 
sions    ....     309 
Bright's  disease  caused  by  al- 
cohol   ....     262 
Bronchial  tubes       .         .         .     205 
Burns  or  scalds       .         .         -375 


Capillaries 

Carbohydrates 

Carpus    . 

Cartilage 

Hyaline    . 
White  fibro- 
Yellow  fibro- 
Thyroid    . 
Arytenoid 
Cricoid     . 

Cells 


•  183 
8,  100 

•  38 
.  18 
.  18 
.  18 
.  18 

•  357 

•  358 

•  358 

9 


and  the  human  organism  10 

Kinds  of  .         .         .         .n 

Vital  properties  of   .         .  1 1 

Epithelial          .         .         .  •    14 

Nerve       ....  264 

Cerebrum        ....  270 

Cerebellum      .         .         .         .271 

Chemical   compounds   in  the 

body     ....  6 

Chloral 303 

Chyle 143 

Chyme 132 

Cilia  of  air  passages        .         .  206 


INDEX. 


441 


Circulation  .  .  .  .169 
General  plan  of  .  .174 
Portal  .  .  .  .186 
Pulmonic  .  .  -185 

Systemic  .         .         .         .185 
Effect  of  alcohol  on          .     193 

Clavicle 37 

Cleanliness,  Necessity  for  .  247 
Clothing,  Use  of  .  .  .252 
Material  used  for  .  .  253 
Suggestions  for  use  of  .  254 
Effects  of  tight-fitting  .  255 
Miscellaneous  hints  on 

use  of  .         .         .         .     256 

Catching,  on  fire      .'         .     376 

Coagulation  of  blood      .         .172 

Cocaine,  ether,  and  chloroform     303 

Cochlea  of  ear         ...     346 

Cocoa in 

Coffee -in 

Colon 136 

Color-blindness  .  .  .  336 
Complemental  air  .  .  .210 
Compounds,  Chemical  .  .  6 
Organic  ....  7 
Condiments  ....  109 
Conjunctiva  ....  334 
Connective  tissue  .  .  1 5 

Consonants  ....  362 
Contagious  diseases  .  .  390 
Contraction,  Object  of  .  -63 
Contusions  and  bruises  .  .  369 
Convulsions  ....  380 

Cooking 115 

Coughing         •         .         .         .220 

Cornea 323 

Corpuscles,  Blood  .         .         -171 

Red 171 

Colorless.  .  .  -171 
Corti,  Organ  of  ...  346 
Cranial  Nerves  .  .  .  275 


Cranium,  Bones  of  27 

Crying     .         .         .  .219 

Crystalline  lens       .         .         .     326 

Cuticle 238 

Cutis  vera,  or  true  skin  .         .     237 

Degeneration,  Fatty,  due  to    . 

alcohol          .         .         .164 

Deglutition,  or  swallowing      .     128 

Deodorants     .         .         .         .401 

Diet,  Important  articles  of      .     103 

Effect  of  occupation  on       151 

Too  generous  .         .         .151 

Effect  of  climate  on         -152 

Digestion,  Purpose  of      .         .     119 

General  plan  of        .         .121 

in  small  intestines    .         -143 

in  large  intestines     .         -144 

Effect  of  alcohol  on       159-162 

Disease,  Effect   of  alcoholics 

upon     ....     232 
Diseases,  infectious  and  con- 
tagious, Management  of     402 
Care  of    .         .         .         .     390 
Hints  on  nursing      .         .     390 
Disinfectants  .         .         .         .401 
Air  and  water  as      .         .401 
How  to  use      .         .         .     403 
Dislocations    .         .         .         -51 
Dogs,  mad,.  Bites  of        .         .     370 
Drowning,  Apparent       .         -381 
Methods  of  treating         .     383 
Sylvester  method     .         .     383 
Marshall  Hall  method      .     384 
Duct,  Hepatic          .         .         -138 
Cystic       .         .         .         .     139 
Common  bile  .         .         .     139 
Thoracic  .         .         .         .146 
Nasal        ....     334 
Duodenum       .         .         .         -134 
Dura  mater     ....     273 


442 


INDEX. 


Ear,  External . 
Middle     . 
Bones  of  the 
Internal  . 


342 

343 
344 
345 


Practical  hints  on  care  of     349 

Foreign  bodies  in     .         -377 

Eating,  Practical  points  about     154 

Eggs  as  food  .         .         .         .104 

Elements,    Chemical,    in    the 

body      ....         5 

Epidermis,  or  cuticle       .         .     238 

Epiglottis         .         .         .      204,  356 

Epithelium      .         .         .  13 

Squamous         .         .  14 

Columnar         .         .         .14 

Glandular         .         .         .      .14 

Ciliated    .        .        .        .14 

EpitheliaF  tissues,    Functions 

of 15 

Erect  position          ...       68 

Ethmoid  bone          ...       28 

Eustachian  tube      .         .         .     343 

Excretion         ....     235 

Exercise,  Physical  ...       78 

Importance  of .         .         .       78 

Effect  of,  on  muscles        .       80 

Effect  of,   on    important 

organs  ....      82 
Effect  of,  on  personal  ap- 
pearance      ...       83 
Effect  of  excessive  .        .      84 
Amount  of,  required        .       87 
Time  for  .         .         .         .89 
Physical,  in  school     .         .     93 
Practical  points  about      .       94 
Effect  of  alcohol  and  to- 
bacco on  .        -95 
Experiments,  Limitations  of   .     405 
Value  of  .         .         .         .     405 

Eye 321 

Inner  structure  of    .         -325 


Eye,  compared  to  camera  .     327 

Refractive  media  of  -328 

Movements  of          .  .     332 

Foreign  bodies  in     .  .     378 

Practical  hints  on  care  of     338 

Effect  of  alcohol  on  .     340 

Effect  of  tobacco  on  -341 

Eyeball,  Coats  of    .         .  .322 

Eyelids  and  eyebrows      .  .     333 

Eyesight  in  schools          .  .     336 


Face 

Bones  of  the     . 
Fainting . 
Fats         .    '     . 

and  oils    . 
Femur     . 
Fibrin      . 
Fibula     . 
Fish  as  food    . 
Food  and  drink 
Food,  why  we  need  it 


29 
29 

380 
8 

101 


42 

104 

97 

97 


Absorption     of,     by    the 

blood    .         .         .         .119 
Quantity  of,  as   affected 

by  age  .  .  .  .  i 50 
Kinds  of,  required  .  .  152 
Foods,  Classification  of  .  .  99 
Nitrogenous  ...  99 
Proteid  ....  99 
Saline  or  mineral  .  .102 
Vegetable  .  .  -105 
Proteid  vegetable  .  -105 
Non-proteid  vegetable  .  106 
Non-pro teid  animal .  .108 
Table  of  .  .  .  .  155 
Food  materials,  Table  of-  .  107 
Composition  of  .  -103 

Foot 42 

Foul  air,  Effect  of,  on  health     222 
Frontal  bone  ....       27 


INDEX. 


443 


Frost  bites 

376 

Hiccough         .... 

219 

Fruits  as  food          .         . 

1  08 

Hip  bones        .... 

35 

Histology  defined    . 

4 

Gall  bladder    .         .         .       '. 

139 

Humerus         .... 

37 

Garden  vegetables  . 

1  08 

Hygiene  defined 

4 

Gastric  glands          .         . 

I31 

Hyoid  bone     .         .         .36, 

357 

Gastric  juice,  Effect  of  alcohol 

Hypermetropia 

330 

on          .... 

161 

Glands     

121 

Ileum       

134 

Mesenteric 

146 

Injured,  Prompt  aid  to    . 

367 

Lymphatic 

147 

Insalivation     .... 

126 

Ductless  .... 

148 

Intestine,  Small 

*34 

Thyroid    .... 

148 

Coats  of  small 

'35 

Thymus    .... 

148 

Large       .... 

136 

Suprarenal 

I49 

Intoxicants,    Physical    results 

Lacrymal 

334 

of          .... 

297 

Glottis     

358 

Iris  of  the  eye          .        - 

326 

Hair        

239 

Jejunum  

134 

Structure  of 

240 

Joints      . 

44 

Hair  and  nails,  Care  of  . 

252 

Imperfect 

46 

Hall,    Marshall,   method    for 

Perfect     .... 

46 

apparent  drowning 

384 

Hinge       .... 

46 

Hand       

38 

Ball-and-socket 

46 

Haversian  canals     . 

25 

Pivot        .... 

46 

Head  and  spine,  how  joined   . 

34 

Head,  Bones  of       ... 

26 

Katabolism  denned 

13 

Hearing,  Sense  of  . 

34i 

Kidneys  

257 

Mechanism  of  . 

347 

Structure  of     ... 

258 

Effect  of  tobacco  on 

35i 

Function  of      ... 

258 

Heart      

176 

Action  of,  how  modified 

259 

Valves  of          .         . 

177 

Effect  of  alcohol  on 

261 

General    plan   of    blood- 

Kidneys and  skin    . 

246 

vessels  connected  with 

179 

Rhythmic  action  of  . 

187 

Lacrymal  apparatus     ,    . 

334 

Impulse  and  sounds  of     . 

187 

gland        .... 

335 

Nervous  control  of  . 

188 

Lacteals  .        .        .        .     '    . 

145 

Effect  of  alcohol  on 

r95 

Landmarks,  Bony   . 

415 

Effect  of  tobacco  on 

198 

Muscular 

4i7 

Heat,  Animal  .... 

225 

heart         .... 

419 

Sources  of        ... 

226 

arteries     .... 

419 

444 


INDEX. 


Larynx    . 

Laughing 

Lens,  Crystalline     . 

Levers  in  the  body 

Life,  The  process  of 

Ligaments 

Limbs,  Upper 
Lower 

Liver        . 

Minute  structure  of 
Blood  supply  of 
Functions  of    . 
Effect  of  alcohol  on 

Lungs      . 

Minute  structure  of 
Capacity  of 
Effect  of  alcohol  on 
Bleeding  from . 

Lymph     . 

Lymphatics 

Mad  dogs,  Bites  of 
Malar  bone     . 
Mastication 
Maxillary,  Superior 

Inferior    . 
Meals,  Hints  about 
Meats  as  food 
Medulla  oblongata . 
Membrane,  Synovial 

Serous 

Arachnoid 
Membranes,  Brain  . 
Mesentery 
Metabolism  defined 
Metacarpal  bones    . 
Metatarsal  bones     . 
Microscope,  Use  of 
Milk        . 
Mineral  foods 
Morphology  defined 


357 

Motion  in  animals  . 

57 

219 

Mouth      

122 

326 

Movement,  Mechanism  of 

66 

67 

Muscles,  Kinds  of  . 

57 

12 

voluntary,  Structure  of     . 

58 

45 

involuntary,  Structure  of 

59 

36 

Arrangement  of 

64 

4i 

Important 

69 

137 

Effect  of  alcohol  on 

72 

137 

Effect  of  tobacco  on 

75 

139 

Review  analysis  of  . 

77 

140 

Rest  for   . 

86 

163 

Muscular  tissue,  Effect  of  al- 

206 

cohol  on       ... 

73 

208 

Changes  in        ... 

79 

210 

Properties  of    .         . 

60 

230 

activity     .... 

79 

374 

contraction 

63 

H7 

fatigue      .... 

85 

H7 

sense         .... 

312 

Myopia  .          .         .     -    . 

330 

370 

29 

Nails       

241 

122 

Care  of     . 

252 

29 

Nasal  bones    .... 

29 

30 

Nerve  cells      .... 

264 

'53 

fibers        .... 

265 

104 

cells  and  fibers,  Function 

273 

of          .... 

266 

45 

Nerves,  Cranial 

275 

176 

Spinal       .... 

278 

273 

Motor       .         .         .189, 

279 

273 

Sensory    .... 

279 

146 

spinal,  Functions  of 

279 

'3 

Nervous  system,  General  view 

40 

of          .... 

263 

43 

compared     to     telegraph 

407 

system  .... 

267 

103 

Divisions  of 

268 

102 

Effect  of  alcohol  on 

294 

4 

Effect  of  tobacco  on 

3°5 

INDEX. 


445 


Nitrogenous  foods  . 

99 

Non-proteid  vegetable  foods  . 

1  06 

animal  foods    . 

108 

Nose,  Bleeding  from 

374 

Foreign  bodies  in     . 

377 

Occipital  bone 

27 

CEsophagus     .... 

128 

Opium     

301 

Poisonous  effects  of 

301 

In  patent  medicines 

302 

Victim  of  the,  habit 

302 

Organic  compounds 

7 

Outdoor  games 

9i 

Oxidation         ...       98, 

226 

Pain,  Sense  of         ... 

313 

Palate  bones   .... 

29 

Pancreas          .... 

141 

Pancreatic  juice 

142 

Parietal  bones 

27 

Patella     .         .         .         . 

42 

Pepsin     

132 

Pericardium     .... 

176 

Periosteum      .... 

25 

Peritoneum      .... 

'35 

Phalanges        .         .         .          40,  43 

Pharynx  and  oesophagus 

128 

Physical  exercise     . 

78 

Physical  education  in  school  . 

92 

Physical  exercises  in  school     . 

93 

Physiology  defined  . 

4 

Study  of  . 

i 

what  it  should  teach 

2 

Main  problems  of,  briefly 

stated  .... 

3 

Physiological  knowledge, 

Value  of       ... 

5 

Pia  mater         .... 

273 

Pneumogastric  nerve       .      189, 

276 

Poisons  

391 

Poisons,  Table  of   .         .         .  393 

Antidotes  for  .         .         .  393 

Practical  points  about      .  394 

Poisoning,  Treatment  of          .  392 

Portal  circulation    .         .         .  186 

Portal  vein      .         .         .         .138 

Presbyopia      ....  330 

Pressure,  Where  to  apply        .  373 

Proteids  .         .         .         .         .  8,  99 

Proteid  vegetable  foods  .         .  105 

Protoplasm      ....  8 

Pulmonary  artery    .         .         .  179 

veins         ....  180 

Pulmonary  infection       .         .  222 

Pulse 192 

Pupil  of  the  eye       .        .        .  323 

Radius 38 

Receptaculum  chyli         .         .146 

Rectum 136 

Reflex  centers  .  .  .282 
in  the  brain  .  .  .  284 
Reflex  action,  Importance  of  .  284 
Renal  secretion  .  .  .259 
Residual  air  .  .  .  .210 
Respiration,  Nature  and  object 

of          202 

Nervous  control  of  .  .  213 
Effect  of,  on  the  blood  .  215 
Effect  of,  on  the  air  .216 
Modified  movements  of  .  218 
Effect  of  alcohol  on  -230 
Effect  of  tobacco  on  .  232 
artificial,  Methods  of  .  383 
Rest,  for  the  muscles  .  .  86 
Need  of  .  .  .  .288 
Benefits  of  ...  289 
The  Sabbath,  a  day  of  .  290 
of  mind  and  body  .  .  389 

Retina 324 

Ribs  and  sternum   ...       34 


446 


INDEX. 


Saline  or  mineral  foods  .  .102 
Saliva  .  .  .  .  .127 
Salt  as  food  .  .  .  .109 
Salts,  Inorganic,  in  the  body  .  7 
Scalds  or  burns  .  .  -375 

Scapula 36 

School,  Physical  eduation  in  .       93 

Positions  at  .         -49 

School  and  physical  education       92 

Secretion         .         .         .         .121 

Semicircular  canals          .         .     346 

Sensations,  General         .         .     307 

Sensation,  Conditions  of         .     309 

Sense,  Organs  of     .         .         -310 

Sense  organ,  The  essentials  of     308 

Serous  membranes .         .         .176 

Sick-room,  Arrangement  of    .     386 

Ventilation  of  .        .        -387 

Hints  for          ...     387 

Rules  for          .         .         .388 

Sighing 219 

Sight,  Sense  of        ...     320 
Skating,  swimming,  and  row- 
ing .         .         .90 
Skeleton          .        .        .        .21 
Review  analysis  of  .  56 
Skeleton  and  manikin,  Use  of     408 
Skin,  The        .        .        .        -236 
regulating  temperature     .     244 
Action  of,  how  modified  .     244 
Absorbent  powers  of        .     246 
and  the  kidneys        .         .     246 

Skull 26 

Sutures  of  .        -3° 

Sleep,  a  periodical  rest    .         .     290 
Effect  of,  on  bodily  func- 
tions    ....     291 
Amount  of,  required         .     292 
Practical  rules  about        .     292 

Smell 317 

Sense  of  .         .         .         .318 


Sneezing          ....     220 

Snoring 219 

Sobbing 219 

Special  senses          .         .         .     307 

Speech 361 

Sphenoid  bone         ...       27 

Spinal  column          .         .  31 

Spinal  cord      .         .         .32,  277 

Structure  of  .         .     277 

Functions  of    .         .         .     279 

conductor  of  impulses      .     280 

as  a  reflex  center      .         .282 

Spinal  nerves  ....     278 

Functions  of    .         .         .     279 

Spleen 148 

Sprains  and  dislocations  .  51 
Stammering  ....  363 
Starches  and  sugars  .  .100 

Sternum 35 

Stomach          .        .        .        .129 

Coats  of  .         .         .         .     131 

Digestion  in  .         -132 

Effect  of  alcohol  on         .160 

-     Bleeding  from .         .  374 

Strabismus      .        .        .        -333 

Stuttering        ....     364 

Sunstroke        .         .         .         -385 

Supplemental  air    .         .         .210 

Suprarenal  capsules         .         .     149 

Sutures  of  skull      ...       30 

Sweat  glands  ....     242 

Sweat,  Nature  of    .         .         .     243 

Sylvester  method  for  apparent 

drowning      .         .         .     383 

Sympathetic  system         .      189,  286 

Functions  of     .         .         .     286 

Synovial  membrane         .         .       45 

sheaths  and  sacs      . '       .       66 


Taste,  Organ  of 
Sense  of  . 


313- 
3*4 


INDEX. 


447 


Taste,      Physiological    condi- 
tions of          .         .         .     315 
Modifications  of  the  sense     317 
Effect  of  alcohol  on         -31? 
Effect  of  tobacco  on         .     317 
Tea          .         .         .         .         .in 
Tear  gland  and  tear  passages     334 

Tears 335 

Technical  terms  denned  .         3 

Teeth       .         .         .         .         .123 

Development  of       .         .124 

Structure  of  .         .124 

Proper  care  of  .         .     1 57 

Hints  about  saving  .         -158 

Temperature,    Regulation    of 

bodily  ....     227 

Skin  as  a  regulator  of      .     228 

Voluntary  regulation  of  .     229 

Sense  of  .         .         .         -312 

Temporal  bones      ...       27 

Tendon  of  Achilles          .          43,  65 

Tendons  .         .         .       , .       65 

Thigh 41 

Thoracic  duct .         .         .         .146 

Throat 356 

Care  of    .        .        .        .     364 

Effect  of  alcohol  on          .     365 

Effect  of  tobacco  on         .     365 

Foreign  bodies  in     .         -377 

Thymus  gland          .         .         .148 

Thyroid  gland          .         .         .148 

Tibia 42 

Tidal  air          ....     210 

Tissue,  White  fibrous      .         .       16 

Connective       .         .  15 

Yellow  elastic  .        .        -17 

Areolar    .         .         .         -17 

Adipose   .         .         .         .18 

Adenoid  .         .         .         .18 

Muscular  ...       60 

Tissues,  Epithelial  .         .       14 


Tissues,  epithelial,  Varieties  of  14 

Functions  of    .         .         .  15 
Connective       .         .         .16 

Tobacco,  Effect  of,  on  bones  54 

Effect  of,  on  muscles        .  75 
Effect     of,    on    physical 

culture          .         .         -95 

Effect  of,  on  digestion     .  165 

Effect  of,  on  the  heart     .  198 

Effect  of,  on  the  lungs     .  232 
Effect  of,  on  the  nervous 

system  ....  305 

Effect  of,  on  the  mind     .  305 

Effect  of,  on  the  character  305 

Effect  of,  on  taste    .         .  317 

Effect  of,  on  hearing        .  351 
Effect  of,  on  throat  and 

voice     ....  365 

Touch,  Organ  of     .         .         .  310 

Sense  of  .         .         .         .  311 

Trachea 203 

Trunk,  Bones  of  .         -30 

Tympanum,  Cavity  of     .         .  343 


Ulna        .... 
Urine       .... 

Valve,  Mitral 
Valves  of  the  heart 
Valves,  Tricuspid    . 

Semilunar 
Vegetable  foods 
Veins       .... 
Ventilation 

Conditions  of  efficient 

of  sick-room     . 
Vestibule  of  ear 
Vermiform  appendix 
Vision,  Common  defects  of 

Effect  of  tobacco  on 
Vivisection  and  dissection 


259 

178 
177 
178 
179 

*°5 

182 
223 
224 

387 

345 
136 
329 
34i 
408 


448 


INDEX. 


Vocal  cords  .  .         .         .         .358 

Voice,  Mechanism  of      .         -359 

Factors  in  the  production 

of          ....     360 

Care  of    .         .         .         .     364 

Effect  of  alcohol  on         -365 

Effect  of  tobacco  on         .     365 

Vowel  sounds          .         .         .     362 

Walking,   jumping,   and   run- 
ning     ....      89 


Waste  and  repair    ...  97 

Waste  material,  Nature  of      .  98 
Waste  products,    Elimination 

of           ....  235 
Water  as  food         .         .      102,110 
Whispering      .         .         .         . .  363 
Wounds,   Incised  and  lacera- 
ted        ....  368 


Yawning 


219 


n 


451.362 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


